Only a small proportion of all systems are shown. Shaded systems have been lost behind the border as Tchicaya arrives on the Rindler, 605 years after Mimosa.

Chapter 4

By choice, Tchicaya's mind started running long before his new body was fully customized. As his vision came into focus, he turned his gaze from the softly lit lid of the crib to the waxen, pudgy template that he now inhabited. Waves of organizers swarmed up and down his limbs and torso like mobile bruises beneath the translucent skin, killing off unwanted cells and cannibalizing them, stimulating others to migrate or divide. The process wasn't painful - at worst it tickled, and it was even sporadically sexy - but Tchicaya felt an odd compulsion to start pummeling the things with his fists, and he had no doubt that squashing them flat would be enormously satisfying. The urge was probably an innate response to Earthly parasites, a misplaced instinct that his ancestors hadn't got around to editing out. Or perhaps they'd retained it deliberately, in the hope that it might yet turn out to be useful elsewhere.

As he raised his head to get a better view, he caught sight of an undigested stretch of calf, still bearing traces of the last inhabitant's body hair and musculature. "Urrggh". The noise sounded alien, and left a knot in his throat. The crib said, "Please don't try to talk yet." The organizers swept over the offending remnant and dissolved it.

Morphogenesis from scratch, from a single cell, couldn't be achieved in less than three months. This borrowed body wouldn't even have the DNA he'd been born with, but it had been designed to be easy to regress and sculpt into a fair approximation of anyone who'd remained reasonably close to their human ancestors, and the process could be completed in about three hours. When traveling this way, Tchicaya usually elected to become conscious only for the final fitting: the tweaking of his mental body maps to accommodate all the minor differences that were too much of a nuisance to eliminate physically. But he'd decided that for once he'd wake early, and experience as much as he could.

He watched his arms and fingers lengthen slightly, the flesh growing too far in places, then dying back. Organizers flowed into his mouth, re-forming his gums, nudging his teeth into new locations, thickening his tongue, then sloughing off whole layers of excess tissue. He tried not to gag.

"Dith ith horrible," he complained.

"Just imagine what it would be like if your brain was flesh, too," the crib responded. "All those neural pathways being grown and hacked away - like a topiary full of tableaux from someone else's life being shaped into a portrait of your own past. You'd be having nightmares, hallucinations, flashbacks from the last user's memories."

The crib wasn't sentient, but pondering its reply made a useful distraction from the squirming sensation Tchicaya was beginning to feel in his gut. It was a much more productive rejoinder than: "You're the idiot who asked to be awake for this, so why don't you shut up and make the best of it?"

When his tongue felt serviceably de-slimed, he said, "Some people think the same kind of thing happens digitally. Every time you reconfigure a Qusp to run someone new, the mere act of loading the program generates experiences, long before you formally start it running."

"Oh, I'm sure it does," the crib conceded cheerfully. "But the nature of the process guarantees that you never remember any of it."

When Tchicaya was able to stand, the crib opened its lid and had him pace the recovery room. He stretched his arms, swiveled his head, bent and arched his spine, while the crib advised his Qusp on the changes it would have to make in order to bring his expectations for kinesthetic feedback and response times into line with reality. In a week or two he would have accommodated to the differences anyway, but the sooner they were dealt with, the sooner he'd lose the distracting sense that his own flesh was like poorly fitted clothing.

The clothes that were waiting for him had already been informed of his measurements, and the styles, colors, and textures he preferred. They'd come up with a design in magenta and yellow that looked sunny without being garish, and he felt no need to ask for changes, or to view a range of alternatives.

As he dressed, Tchicaya examined himself in the wall mirror. From the whorl of dark bristles on his scalp to the glistening scar running down his right leg, every visible feature had been reproduced faithfully from a micrometer-level description of his body on the day he'd left his home world. For all he could tell, this might as well have been the original. The internal sense of familiarity was convincing, too; he'd lost the slight tension in his shoulder muscles that had been building up over the last few weeks before his departure, but having just rid himself of all the far more uncomfortable kinks he'd acquired in the crib, that was hardly surprising. And if this scar was not the scar from his childhood, not the same collagen laid down by the healing skin in his twelve-year-old body, nor would it have been the same in his adult body by now, if he'd never left home. All an organism could do from day to day was shore itself up in some rough semblance of its previous condition. The same was true, from moment to moment, for the state of the whole universe. By one means or another, everyone was an imperfect imitation of whatever they'd been the day before.

Still, it was only when you traveled that you needed to dispose of your own past, or leave behind an ever-growing residue. Tchicaya told the crib, "Recycle number ten." He'd forgotten exactly where the tenth-last body he'd inhabited was stored, but when his authorization reached it, the memories sitting passively in its Qusp would be erased, and its flesh would be recycled into the same kind of waxen template as the one he'd just claimed as his own.

The crib said, "There is no number ten, by my count. Do you want to recycle number nine?"

Tchicaya opened his mouth to protest, then realized that he'd spoken out of habit. When he'd left Pachner, thirty years before - a few subjective hours ago - he'd known full well that his body trail would be growing shorter by one while he was still in transit, and he wouldn't have to lift a finger or say a word to make it happen.

He said, "Keep number nine."

As he stepped out of the recovery room, Tchicaya was grateful for his freshly retuned sense of balance. The deck beneath his feet was opaque, but it sat inside a transparent bubble a hundred meters wide, swinging for the sake of gravity at the end of a kilometer-long tether. To his left, the ship's spin was clearly visible against the backdrop of stars, all the more so because the axis of rotation coincided with the direction of travel. The stars turning slowly in the smallest circles were tinted icy blue, while away from the artificial celestial pole they took on more normal hues, ultimately reddening slightly. The right half of the sky was starless, filled instead with a uniform glow that was untouched by the Doppler shift, and so featureless that there was nothing to be seen moving within it: not one speck of greater or lesser brightness rising over the deck in time with the stars.

From the surface of Pachner, the border of the Mimosa vacuum had appeared very different, a shimmering sphere of light blazing a fierce steely blue at the center, but cooled toward the edges by its own varied Doppler shift. The graded color had made it look distinctly rounded and three-dimensional, and the fact that you could apparently see it curving away from you had added to an already deceptive impression of distance. Because it was expanding at half the speed of light, the amount of sky the border blotted out was not a reliable measure of its proximity. Looking away from its nearest point meant looking back to a time when it had been considerably smaller, and starlight that had grazed the sphere centuries before - skirting the danger, and appearing to delineate it - actually told you nothing about its present size. When Tchicaya had left, Pachner had been little more than two years away from being engulfed, but the border had barely changed its appearance in the decade he'd spent there, and it would still have occupied a mere one hundred and twenty degrees of the view at the instant the planet was swallowed.

Tchicaya had been on Pachner to talk to people on the verge of making their escape. He'd had to flee long before the hard cases, who'd boasted that they'd be leaving with just seconds to spare, but as far as he knew he'd been the only evacuee who was planning to end up closer to the border than when he left. Doomed planets were useless as observation posts; no sooner did the object of interest come near than you had to retreat from it at the speed of light. The Rindler was constantly retreating, but no faster than was absolutely necessary. Matching velocities with the border transformed its appearance; from the observation deck, the celestial image that had become an emblem of danger for ten thousand civilizations was nowhere to be seen. The border finally looked like the thing it was: a vast, structureless, immaterial wall between two incomparably different worlds.

"Tchicaya!"

He looked around. There were a dozen people nearby, but they were all intent on the view. Then he spotted a lanky figure approaching, an arm stretched up in greeting. Tchicaya didn't recognize the face, but his Mediator picked up a familiar signature.

"Yann?" Tchicaya had known for centuries that Yann was also weaving his way toward the Rindler, but the last place he'd expected to run into him was the observation deck. In all the time they'd been in contact, exchanging messengers across decades and light-years, Yann had been strictly acorporeal.

The half-stranger stood before him. "How are you?"

Tchicaya smiled. "I'm fine. You seem to have put on weight."

Yann shrugged apologetically. "Conforming to local fashions. I still think it's an absurdity: boosting millions of tonnes of furniture into a trajectory like this, when a few hundred kilograms of instrumentation and Qusps could have achieved as much. But given that they've gone ahead and done it anyway, and given that most of the people here are wearing flesh, I have to take account of that. I need to be in the thick of things, or there's no point being here at all."

"That makes sense," Tchicaya conceded. He hated the idea of anyone being forced out of their preferred mode, but the political realities were undeniable.

If the optimists were right, and the border's current velocity was the highest it would ever be, the simplest way to avoid the threat would be to flee from it. If your whole world already consisted of compact, robust hardware that was designed to function in interstellar space, the prospect of engineering in the necessary shielding against relativistic collisions with gas and dust, accelerating to a suitable velocity - half c plus a chosen safety margin - then simply coasting away from the danger, was not unthinkable at all. A dozen acorporeal communities, and countless scattered individuals, had already done that.

For people accustomed to dwelling on a planetary surface, though, the notion of entering a permanent state of flight was more likely to be horrifying. So far, the Mimosan vacuum had swallowed more than two thousand inhabited systems, and while most of the planet-hopping refugees were willing to transmit themselves at lightspeed from point to point, in less than two millennia all the old, established colony worlds that had taken them in would themselves be gone. In principle, the process could be prolonged indefinitely: new, habitable planets could be prepared in advance by high-velocity spore packages, with people following close behind. Each temporary home would last a little longer than the one before, as the border was outpaced. People might even grow accustomed to the fact that every world they set foot upon would be obliterated, not in billions of years, but in a few thousand. It would take six times as long as recorded history before the entire Milky Way was lost, and by then, the gulf between neighboring galaxies might seem less daunting.

Even assuming a watertight proof, though, that the border would not speed up without warning and turn that whole scenario into a rosy-hued fantasy, exile was not a fate to be accepted lightly. If it was physically possible to turn back the novovacuum - to seed its destruction, the way the Mimosans had seeded its creation - Tchicaya's fellow embodied had by far the greatest stake in making that happen. It was not going to be easy to persuade them that they shouldn't try.

Yann said, "You've just come from Pachner?"

Tchicaya nodded. He was pleased to have met up with Yann, but he was having trouble maintaining eye contact; the spinning sky kept drawing his gaze. "When did you get here?" He'd lost track of Yann's recent movements; communication between interstellar travelers had always been difficult, with line-of-sight time lags and transit insentience, but having to route signals around a constantly growing obstacle had added a further level of delays and fragmentation.

"Almost nine years ago."

"Ha! And there I was thinking you were the one out of your element."

Yann took a moment to interpret this. "You've never been in space before?"

"No."

"Not even planetary orbit?" He sounded incredulous.

Tchicaya was annoyed; it was a bit rich for a former acorporeal to put such stock in where he had or hadn't been, in the flesh. "Why would I have been in space? Vacuum never used to be much of an attraction."

Yann smiled. "Do you want to take the grand tour, while I fill you in?"

"Definitely." Everything Tchicaya had heard about the state of play on the Rindler was out of date - though not by the full sixty years that his thirty-year journey would normally have implied. He did a quick calculation before confirming the result with the ship: fifty-two years had elapsed here, since the last bulletin that he'd received on Pachner had been sent.

Stairs led down from the observation deck to a walkway. The ship was made up of sixteen separate modules arranged in a ring; the tethers joining them to the hub were not traversable, but there were umbilicals linking adjacent modules. Once they'd left the shelter of the deck behind, Tchicaya could see the engines sitting at the hub as dark outlines clustered at the zenith. They were unlikely to be used again for some time; if the border suddenly accelerated, it would probably move too fast for the Rindler to escape, and everyone onboard would evacuate the way they'd arrived: as data. Even if the ship was destroyed without warning, though, most people would only lose a few hours' memories. Tchicaya had instructed his Qusp to transmit daily backups, and no doubt Yann was doing something similar, having escaped from the Mimosan vacuum once already that way.

The view from the narrow walkway was disorienting; without an expanse of deck imposing a visual horizon, the rim of the border became the most compelling cue. Tchicaya began to feel as if he was walking inside a huge horizontal centrifuge, hovering an indeterminate distance above an ocean shrouded in white fog. Any attempt to replace this mildly strange hypothesis with the idea that he was actually keeping pace with a shock wave six hundred light-years wide did nothing to improve his steadiness.

"The factions have names now," Yann began.

Tchicaya groaned. "That's a bad sign. There's nothing worse than a label, to cement people's loyalties."

"And nothing worse than loyalties cementing while we're still in the minority. We're Yielders, they're Preservationists."

"Yielders? Whose idea was that?"

"I don't know. These things just seem to crystallize out of the vacuum."

"With a little seeding from the spin doctors. I suppose it's a step up from being Suicidal Deviants, or Defeatist Traitors."

"Oh, those terms are still widely used, informally."

Without warning, Tchicaya's legs buckled. He knelt on the walkway and closed his eyes. He said, "It's all right. Just give me a second."

Yann suggested mildly, "If the view's that unsettling, why not paste something over it?"

Tchicaya scowled. His vestibular system wanted him to curl up on the ground, block out all the contradictory visual signals, and wait for normality to be restored. He spread his arms slightly, reassuring himself that he was prepared to take action to recover his balance at short notice. Then he opened his eyes and rose to his feet. He took a few deep breaths, then started walking again.

"Both stances remain purely theoretical," Yann continued. "The Preservationists are no more prepared to erase the Mimosan vacuum than we are to adapt to it. But the team working on the Planck worms has just attracted a fresh batch of recruits, and they're running experiments all the time. If it ever does come down to a technological race, it's sure to be a close one."

Tchicaya contemplated this prospect glumly. "Whoever first gains the power to impose their own view decides the issue? Isn't that the definition of barbarism?" They'd reached the stairs that led up to the deck of the next module. He gripped the rails and ascended shakily, relieved to be surrounded by the clutter of ordinary objects.

They emerged at the edge of a garden, engineered in a style Tchicaya hadn't seen before. Stems coiled in elaborate helices, sprouting leaves tiled with hexagonal structures that glinted like compound eyes. According to the ship, the plants had been designed to thrive in the constant borderlight, though it was hard to see how that could have required some of their more exotic features. Still, the embellishments did not seem overdone here. Purebred roses or orchids would have been cloyingly nostalgic in the middle of interstellar space.

There were more people in the garden than on the observation deck. When strangers caught his eye, Tchicaya smiled and offered whatever gestures his Mediator deemed appropriate to greet them in passing, but he wasn't ready for formal introductions, sorting everyone into opposing camps.

"Isn't there a level where both sides can still cooperate?" he asked. "If we can't agree on the theory that's going to underpin whatever action finally gets taken, we might as well all give up and join the wagon train to Andromeda."

Yann was apologetic. "Of course. Don't let my moaning give you too bleak a picture. We haven't reached the point of hostility for its own sake; we still pool resources for the basic science. It's only the goal-directed experiments that make things a little frosty. When Tarek started scribing graphs at the border that he believed stood a good chance of being viable proto-worms, we cut him out of all the theoretical discussion groups and data sharing agreements - though none of us thought he was in any danger of succeeding. Since then, he's backed off slightly, and agreed to limit himself to graphs that can test his hunches without running amok if they happen to confirm them."

Tchicaya began to protest, but Yann cut him off. "Yes, I know that's a treaty full of holes: it wouldn't take much disingenuousness to pretend that success was just a terrible mistake. But who am I to lecture anyone about the results they should or shouldn't have expected?"

Tchicaya muttered, "Everyone's wise about the accident, after the fact." He'd met people who'd claimed they'd happily obliterate every extant version of Cass and her accomplices, though that was the rare, extremist view. More commonly, it was conceded that the Mimosans had been cautious, and could not be judged by the magnitude of the force they'd unleashed. Few people could honestly claim that in the Mimosans' place, they would have treated the Sarumpaet rules - inviolate for twenty thousand years - as being subject to serious doubt, let alone erasure.

The last Tchicaya had heard, seventeen people out of the billions of evacuees had chosen to stand their ground and die. He knew that these suicides weighed on Yann's conscience - as did the distress of all those who'd been driven from their homes - but that didn't dictate his attitude to the phenomenon. It might have been tactful to withdraw from the debate entirely, as the other seven had, but Tchicaya understood his refusal to do so. The fate of the vacuum had to be argued on its merits, not treated as a surrogate through which its creators could be condemned or absolved, and Yann intended the fact that he'd dared to take sides to highlight that distinction.

"So there's been no theoretical progress while I was in transit?" A definitive breakthrough would have been the first thing Yann mentioned, but there might still have been promising developments.

Yann shrugged. "Three steps left, four steps down. We scribe these elaborate probe graphs and drop them through the border, then hope that whatever we can see of their decay will tell us something useful. Even when we make an inspired choice of probe and get a clean set of data, as evidence for competing models it's all hideously indirect."

In the immediate aftermath of the accident, it had been easy to devise candidates for meta-rules that stabilized both the old and new vacuum in bulk. In those days, the theorists' biggest problem had been an excess of possibilities. The borderlight's spectrum had helped narrow the choices somewhat, and even the single, fortunate fact that the border was traveling slower than light had ultimately been shown to rule out a class of theories in which the accident had merely changed some particle masses and triggered a boring old Higgs field collapse. In that case, the Mimosan vacuum would have been nothing but a lower-energy version of the ordinary vacuum, and coming to terms with its physics would have been as simple as altering a few numbers in the old equations. A careful analysis, though, had eventually confirmed most people's instinctive hunch: any single kind of vacuum - even one that was undergoing such a collapse - had to appear exactly the same to anyone who was coasting through it, an ancient principle known as Lorentz invariance, dating back to the abolition of the aether. The only velocity at which a change could spread while satisfying that criterion was lightspeed.

Since the Rindler had provided a stable platform from which to probe the border experimentally - while vividly driving home the point that it was not Lorentz-invariant - the embarrassment of riches had proved illusory. Once it had become possible to put the new theories to the test, the only ones that hadn't been falsified were those that remained too ill-defined to offer clear predictions. That provisional vagueness wasn't necessarily a flaw, though; it could easily be the case that the correct grand generalization of the Sarumpaet rules simply couldn't be pinned down from one example of a stable vacuum and a murky glimpse of another, and it was better to be forced to confront that fact than to be lulled for a second time into a false sense of security.

Yann said thoughtfully, "I suppose we could always stop messing about trying to peek behind the border, and just resurrect the Quietener." He punched his hands together enthusiastically. "A few well-planned experiments in the old style might cut straight to the heart of things."

"Oh, that's a great idea. We could do it right here." A second seeding of the novo-vacuum, from a starting point that was already moving rapidly in the same direction as everyone who was fleeing the first, would be twice as difficult to escape. Yann's sardonic suggestion was sobering, though, since it was far from being the only way in which the disaster might be magnified. However careful they were, whatever their motives, there was always the chance of simply making things worse.

"We're dropping the next probe in about twelve hours' time," Yann said. "If you're interested, I could probably swing it."

"Swing what?"

"Bringing you along."

Tchicaya's throat tightened. "You mean, you go down there? In person?"

"Absolutely."

"Why?"

Yann laughed. "Don't ask me! You're the one with the flesh fetish; I thought you'd understand. That's how they do things here. I just play along."

Tchicaya looked past him, into the opaque pearly light, more featureless than any darkness he'd ever encountered. The eyes relished darkness, conjuring up hints of what it might contain, but the borderlight flooded his vision with incontrovertible blankness.

And he believed he could live in that light? He believed the embodied should end their flight, end their resistance, and march straight into that blinding whiteness?

The borderlight was a surface phenomenon, a distractingly perfect veil. Whatever lay behind it could easily be as richly structured and complex as the universe he knew.

He said, "Let me sleep on it."

Half the Rindler's sixteen modules were devoted to accommodation. The ship informed Tchicaya of the cabin he'd been allocated, but he declined detailed directions, since Yann seemed eager to continue as his guide.

"I'll show you where I am, myself, first," Yann offered. "It's on the way, and you're always welcome to drop by." The accommodation modules were all split into multiple levels; away from the edges, where you could still glimpse the sky, it was like being in a high-rise building. When they left the stairwell, Yann paced briskly down a corridor, and pointed out the room.

Tchicaya's heart sank. The cabin was divided into two banks of narrow slots, each about a meter wide and half as high. A number of the slots contained inert figures. Rows of handholds between the pigeonholes were apparently intended to assist the occupants in gaining access. Yann followed his gaze and said, "It's not that hard, once you're used to it." He demonstrated, clambering up and sliding into his coffin-sized bunk, the fifth in a stack of eight.

Tchicaya said forlornly, "My embodiment request had the standard clause: if there was no room for me here at full size, the ship was meant to bounce me to the nearest alternative destination. Maybe I'm going to have to start spelling out the meaning of some of those terms." In four millennia of traveling between planetary surfaces, he'd encountered a wide range of living conditions deemed acceptable by the local people, whether through custom or necessity. On rare occasions, he'd even been provided with deliberately inhospitable accommodation. He'd never seen people squeezed together as tightly as this.

"Mmm." Yann's response was noncommittal, as if in retrospect he wasn't surprised by the complaint, but it honestly hadn't occurred to him that a newcomer would see the Rindler as cramped. He deftly reversed his insertion maneuver and joined Tchicaya on the deck.

"I'd suggest they ease things by scrapping the garden," Tchicaya mused, "but given how little difference that would make, they probably should keep it, for sanity's sake."

Yann squeezed past him, back into the corridor. Tchicaya trudged after him dejectedly. He'd felt no sense of panic upon waking in the confinement of the crib, but he hadn't realized he'd soon be moving into something smaller.

He crossed the final walkway with his eyes locked straight ahead, still faltering every ten or fifteen meters when the false horizon became impossible to ignore. He was angry that he was letting these petty tribulations weigh on him. He was lucky: he was used to travel, he was used to change, and he should have been inured to this kind of minor disappointment. Most of the evacuees on the verge of leaving Pachner had lived there all their lives, and change of the kind they were about to confront was something metaphysically foreign to them. Never mind what lay behind the borderlight; those people knew the shape of every rock within a thousand-kilometer radius of their homes, and even if they ended up on a world miraculously similar by any planetologist's standards, they'd still feel alienated and dispossessed.

As they climbed the stairs, Tchicaya joked, "Let's head back to the garden. I can sleep in the bushes." His shoulders were already aching at the thought of having to lie so still. He could modify himself to lose his usual urge to turn over repeatedly as he slept, but the prospect of needing to do that only made him feel claustrophobic in a deeper sense. You could whittle away a hundred little things like that, and not miss any of them individually, but then you woke one day to find that half your memories no longer rang true, every minor joy and hardship drained of its flavor and significance.

"D37, wasn't it?" Yann asked cheerfully. "That's left here, then fourth door on the right." He stopped and let Tchicaya walk past him. "I'll talk to you again soon about the probe drop, but I'm sure the others won't object."

"Yeah. Thanks." Tchicaya raised a hand in farewell.

The doors he passed were all closed, but the fourth recognized him and opened to his presence.

In front of him stood a desk, two chairs, and a set of shelves. He stepped into the room, and saw one, quite spacious, bed. Behind a partition, there was a shower, toilet and basin.

He sprinted after Yann, who started fleeing halfheartedly, then gave up and doubled over with laughter.

"Bastard!" Tchicaya caught up with him, and thumped him on the arm, hard enough to elicit a satisfying yelp.

"Show some cultural sensitivity!" Yann pleaded. "Pain isn't part of my traditional gestalt." Which made it unlikely that he'd actually felt any; even among the embodied, it was a shade conservative to let anything short of structural damage register as genuine discomfort.

"Nor is space, apparently."

Yann shook his head, and tried to appear earnest. "On the contrary. I've always had a sophisticated self-and-environment map; us ex-acorporeals just aren't hung up about its correlations with the physical world. Whatever it looks like to you, what we experience in that crowded cabin is ten orders of magnitude beyond any luxury you've ever known." He said this without a trace of gloating or pomposity. It wasn't hyperbole, or wishful thinking; it was simply true.

"You know I almost turned around and left the ship?"

Yann snickered, completely unconvinced.

Tchicaya was at a loss for any suitable parting threat, so he just raised his arms in resignation and walked back to his cabin.

Sweeping his gaze around the modest few square meters made him beam like an idiot. It was one-thousandth the size of the house he'd lived in on Pachner, but it was everything he needed.

"Bastard." He lay down on the bed and thought about revenge.

The shuttle separated from the Rindler, sending Tchicaya's stomach into free fall. He watched the docking module retreat, knowing full well that he'd been flung off at a tangent, backward, but so viscerally convinced that he'd fallen straight down that the sight of the module - continuing along its arc of rotation, yet dropping from the zenith in front of him rather than disappearing behind his head - scrambled his sense of balance and direction completely. At first he felt as if he was tumbling backward, which would at least have explained what he was seeing, but when his inner ears failed to confirm the motion, the illusion vanished - only to return a moment later, to take him through the same cycle again. The lurching fits and starts that followed might have made him less queasy if they'd actually been happening; it was the inability to make sense of his perceptions that was disturbing, far more than any direct, physical effect of the lack of gravity.

He began to get his bearings once the whole ship was visible, edge-on. A minute later it had shrunk to a sparse necklace of glass beads, and the newly fixed stars finally crystallized in his mind as cues worth taking seriously. The infinite plane of whiteness on his right might have been a moonlit desert seen through half-closed eyes. He'd once flown a glider high over sand dunes at night, on Peldan, nearly free-falling at times in the thin air. There'd been no moonlight, of course, but the stars had been almost as bright as these.

Yann, sitting beside him, caught his eye. "You okay?"

Tchicaya nodded. "In the scapes you grew up in," he asked, "was there a vertical?"

"In what sense?"

"I know you said once that you didn't feel gravity...but was everything laid out and connected like it is on land? Or was it all isotropically three-dimensional - like a zero-gee space habitat, where everything can connect in any direction?"

Yann replied affably, "My earliest memories are of CP4 - that's a Kähler manifold that looks locally like a vector space with four complex dimensions, though the global topology's quite different. But I didn't really grow up there; I was moved around a lot when I was young, to keep my perceptions flexible. I only used to spend time in anything remotely like this" - he motioned at the surrounding, more-or-less-Euclidean space - "for certain special kinds of physics problems. And even most Newtonian mechanics is easier to grasp in a symplectic manifold; having a separate, visible coordinate for the position and momentum of every degree of freedom makes things much clearer than when you cram everything together in a single, three-dimensional space."

So much for being a seasoned traveler. Tchicaya didn't envy Yann's upbringing, but it probably rendered the world behind the border less exotic to him than the notion of a jungle had been to Tchicaya as a child. It shook his confidence to be reminded that there were measures by which his millennia of experience had been laughably narrow.

He couldn't have it both ways, though: he couldn't claim that the embodied needed the shock and the strangeness of this burgeoning universe, and then wish it could be no more daunting to confront than one more mundane planetary surface.

Kadir turned around and interjected testily, "I can analyze the flows in a symplectic manifold perfectly well without pretending to inhabit it. That's what mathematics is for. Imagining that you need to float through every last abstract space that shows up in a physics problem is just being literal-minded."

Yann smiled, unoffended. "I'm not going to argue with you. I haven't come here to proselytize for acorporeality."

Zyfete, seated in front of Tchicaya, muttered, "Why bother, if you can render embodiment just as barren?"

Tchicaya bit his tongue. He'd been forewarned about the level of acrimony, and at some point everyone on the Rindler was going to have to wade waist-deep through their opponents' venom on their way to a resolution, but spur-of-the-moment bickering in a confined space wasn't his idea of productive disharmony.

The shuttle's drive kicked in, delivering a mild push that Tchicaya succeeded in interpreting as a precipitous dive, rather than a complete inversion of land and sky. He scanned the eye-watering whiteness, hunting for their destination, but the glare was impenetrable. It seemed miraculous to be skimming kilometers above an object that dominated the sky for hundreds of light-years - without being burnt to a cinder, as he would have been this close to the surface of a star - but it was sheer size that made the border visible from afar. Each square kilometer didn't have to blaze fiercely for the total luminosity to outshine any supernova. Without the usual Doppler shift to boost the light's power, a pinhole view looking straight at the border would actually have been dimmer, here, by a factor of three, than the equivalent view from any planet he'd visited. What dazzled was the fact that it filled his vision, leaving room for nothing else. On Pachner, for much of the year the border had been partly hidden by daylight, but even when it reached its furthest angle from the sun there'd always been a narrow strip of washed-out darkness left over somewhere on the horizon, with a few pallid stars on which to rest your eyes.

As the drive reversed, he finally spotted the silhouette of the Scribe. He made a mask against the surrounding glare with his hands, and managed to discern some structure. At the top of the machine was a sphere, rainbow iridescent in the light that grazed it. He knew it was embossed with a fine pattern of microjets, trillions of tiny devices capable of firing as few as one or two atoms in any direction. While the Rindler could keep pace with the border well enough simply by cruising, the Scribe's stylus hovered so close that collisions with interstellar gas, and even the pressure of the borderlight itself, would have ruined the alignment if left uncompensated. Presumably, the visitors' own influence would be well within the machine's defensive capacities, but to Tchicaya it was both marvelous and comical that their presence could be accommodated - like a calligrapher inscribing Gravitation on the head of a pin, while four fat infants clambered onto the artisan's shoulders and proceeded to wrestle.

As the shuttle drew nearer, the Scribe's modest size became apparent; it was smaller than one of the Rindler's modules, forty or fifty meters across, with the sphere of microjets held out on a boom above a flat deck. The shuttle's drive made one last perceptible correction before a series of maneuvers too gentle to feel brought them into contact with the deck.

Kadir unstrapped himself, and approached the hatch in the floor of the shuttle. Tchicaya followed him.

"You keep an atmosphere in there?"

Kadir nodded. "People come and go, it's easiest just to maintain the pressure."

Tchicaya frowned. "I'm never going to get to use this, am I?" He pinched the back of his hand to tug on the near-invisible membrane that he'd sprayed all over his skin; he'd been told it would let his body survive for up to a week in vacuum, and since it took three months to grow a new one, that had seemed like a precaution worth taking. The one thing the suit lacked was reaction mass. If he found himself drifting toward the border, the best thing to do would be to broadcast a final backup and resign himself to an interesting local death.

Kadir said, "I'll see if I can arrange an opportunity on the way back." The remark was delivered without obvious malice, but it was still hard to know how to take it. Since Tchicaya had allowed Yann to introduce him to the two Preservationists as a fellow partisan, the tension he'd felt had ebbed and flowed, and he was never sure when to expect a bit of good-natured teasing, and when to brace himself for a genuinely chilly rebuff as an enemy of the cause.

Zyfete and Yann joined them as the hatch irised open, revealing a softly lit tunnel lined with handholds. Tchicaya hung back until last, not wanting to block anyone's progress if he froze. The others all went feetfirst, as if they were descending a ladder, but he felt more secure crawling along the tunnel, imagining himself more or less horizontal. He recalled a playground back on Turaev, a maze of interconnected pipes. When Zyfete glanced up at him and scowled, he poked his tongue out at her and recited a few lines of childish rhyme. In spite of herself, she smiled.

The Scribe's control room was octagonal, with eight slanted windows facing down toward the border. Judging the distance by eye was difficult, with no texture to the light to set the scale, but Tchicaya guessed he was now floating just five or six meters from the novo-vacuum. He suddenly noticed the beating of his heart, though the rhythm didn't feel abnormal; it was a shift in his attention, rather than a rush of adrenaline. He wasn't afraid, but he was acutely aware of his body: the softness and fragility of it, compared to most other things in the world. It was the way he felt when he found himself stranded in the middle of a harsh landscape, insufficiently prepared for its rigors, but not so threatened that he'd simply write off his current incarnation as unsalvageable. It would take a cosmic disaster even larger than Mimosa to rob him of more than a few minutes' memories, but while he inhabited a body he identified with it wholly. He was in a place where a mishap could shred him into something smaller than atoms, and under the circumstances he was more than happy to let instincts predicated on absolute life and death come to the fore and do their best to protect him.

A bank of displays in the center of the room surrounded an octagonal dome, the housing for the stylus. Tchicaya watched as Kadir and Zyfete issued a long series of spoken commands. The lack of automation was almost ritualistic; he glanced inquiringly at Yann, who whispered, "It's a kind of transparency. There are more sophisticated ways we could monitor each other, but having observers from both sides at every experiment, and controlling everything with words, keeps the proceedings out in the open on one level - while we check the equipment and audit the software with a thousand different kinds of high-powered tools, offstage."

"That's so much like Earth-era diplomacy it's depressing."

Yann smiled. "I knew your arcane knowledge would come in handy here."

Tchicaya snorted. "Don't look at me to spout Machiavelli. If you want that shit, go and dig up an ancient."

"Oh, I'm expecting anachronauts to arrive at the Rindler any day now - preceded by a few megatonnes of fusion by-products - and announce that they've come to save the universe."

"Any day, or any millennium." It was an eerie prospect to contemplate. Scattered remnants of pre-Qusp civilization, twenty thousand or so years old, still chugged between the stars in spluttering contraptions, spewing spent fuel and taking thousands of years for every journey. Tchicaya had never met any of the ancients himself, but his father had encountered one group, which had visited Turaev long before he was born. None had traveled more than eighty light-years from Earth, so as yet they hadn't been endangered by the novo-vacuum, but unless the Preservationists triumphed, within decades the anachronauts would face a decision between adopting some of the hated new technologies and annihilation.

Kadir shot them a disapproving look, as if their chattering meant they weren't taking their monitoring role seriously. Tchicaya had full-sensory recall, regardless of conscious attention, and Yann would undoubtedly boast something even fancier, but he disciplined himself and fell silent.

Zyfete was describing a sequence of particles to be emitted by the stylus. The disaster at Mimosa had provided at least one compensatory boon: experiments in quantum gravity had become far easier to perform. The border was only a few Planck lengths deep, providing experimenters with a tool compared to which an atomic blade would look wider than a planetary system. While the highest-energy particles the Scribe could create were laughably blunt instruments, the border itself could be made to carve them into shrapnel vastly more effective than each innocuous whole. When the stylus fired a coherent beam of mesons at the border, the razor wire of disrupted graphs sliced fragments of their own surreal dimensions from the knot of virtual quarks and gluons making up each meson, and it was possible to exploit coherence effects to make some of these fragments act in unison to modify the border itself. Natural sources of noise had no prospect of accidentally triggering the same effect, so the kind of exorbitant shielding the Quietener had used was no longer required.

Kadir turned to look at them inquiringly. Yann nodded approval. "That's all as we agreed. Go ahead."

Zyfete addressed the Scribe. "Execute that."

With no perceptible delay, the Scribe began to answer with the results. Tchicaya's skin tingled; he'd had no time to remind himself between risk and reprieve, but they'd just tickled a tiger that might have responded by raking the four of them into geometric quanta, swallowing the Rindler a fraction of a millisecond later, and redoubling its efforts to devour all their distant backups and more prudent friends.

Kadir started cursing, his Mediator politely tagging the words with a cue that would shut off translation for anyone inclined to be offended. Zyfete watched him, anguished but silent.

When the tirade stopped, Tchicaya asked cautiously, "Not what you were hoping for, but did it tell you anything?"

Kadir kicked the stylus housing, the recoil driving him back to hit the window behind him with a thud. Tchicaya couldn't help wincing; however robust the participants in these collisions, precision machinery, living flesh, and windows facing interstellar vacuum all seemed to merit gentler treatment.

Zyfete said, "This sequence was meant to confirm a previous experiment, but it didn't yield the same results as the last time we ran it. Our model can't explain the discrepancy, either as a statistical variation, or any predictable change in the novo-vacuum."

Kadir turned and blurted out, "Either you genocidal traitors have corrupted this machine, or - "

Yann pleaded, "Or what? Give us the more likely alternative!"

Kadir hesitated, then smiled grimly. "I think I'll keep that hypothesis to myself."

Tchicaya was dismayed, though he was prepared to put the outburst down to frustration, rather than genuine contempt. Both sides were equally helpless. If this went on, no one was going to get their own way, and no one was going to forge a compromise. The novo-vacuum would simply roll on over them.

Halfway back to the Rindler, Kadir apologized. Tchicaya didn't doubt his sincerity, though the words were more formal than friendly. Yann tried to joke with him, making light of the incident, but Kadir withdrew from the conversation.

When they reached the dock and disembarked, the group broke apart. Yann wanted to observe some tests on a new spectrometer package that were being conducted in a workshop higher up in the same module, but Tchicaya didn't feel like tagging along, so he headed back toward his cabin.

He hadn't expected to witness a breakthrough on the trip, let alone gain some kind of dramatic insight himself from mere proximity to the border; he might as well have hoped to learn the secrets of the ordinary vacuum by gazing into thin air. Nevertheless, he felt a pang of disappointment. Before he'd arrived, there'd been an undeniable thrill to the notion of cruising just beyond reach of the fatal shock wave, and then compounding the audacity by turning around and studying it. Dissecting the danger, laying it bare. It was like a legend his mother had told him: in the Age of Barbarism, when humans had rained bombs on each other from the sky, people called Sappers had dived from airplanes to fall beside them and defuse them in midair, embracing the devices like lovers as they reached into their mechanical hearts and seduced them into betraying their malign creators. But if aerodynamics rendered this romantic fable unlikely, at least no one had expected the Sappers to teach themselves nuclear physics from scratch as they fell, then reach inside each atom of fissile material and pluck out the destabilizing protons one by one.

Zyfete caught up with Tchicaya on the stairs leading down to the walkway. She said, "Kadir's home is this far away from the border." She held up her hand, thumb and forefinger almost touching. "Nine thousand years of history. In less than a year, it will be gone."

"I'm sorry." Tchicaya knew better than to respond with platitudes about history living on in memory. He said, "Do you think I want to see Zapata destroyed?" She didn't need to name the planet; everyone knew the awful schedule by heart. "If we can halt the border without wiping out the entire novo-vacuum, I'll back that. I'll fight for that as hard as anyone."

Zyfete's eyes flashed angrily. "How very evenhanded of you! You'd let us keep our homes, so long as there was no danger of you losing your precious new toy!"

"It's not a toy to me," Tchicaya protested. "Was Zapata a toy nine thousand years ago, when it lay on the frontier?"

"That frontier spread out from Earth, and it was made up of willing settlers. It didn't incinerate anyone who dared to stay put." She scowled. "What do you think you're going to find in there? Some great shining light of transcendence?"

"Hardly." Transcendence was a content-free word left over from religion, but in some moribund planetary cultures it had come to refer to a mythical process of mental restructuring that would result in vastly greater intelligence and a boundless cornucopia of hazy superpowers - if only the details could be perfected, preferably by someone else. It was probably an appealing notion if you were so lazy that you'd never actually learned anything about the universe you inhabited, and couldn't quite conceive of putting in the effort to do so: this magical cargo of transmogrification was sure to come along eventually, and render the need superfluous.

Tchicaya said, "I already possess general intelligence, thanks. I don't need anything more." It was a rigorous result in information theory that once you could learn in a sufficiently flexible manner - something humanity had achieved in the Bronze Age - the only limits you faced were speed and storage; any other structural changes were just a matter of style. "All I want to do is explore this thing properly, instead of taking it for granted that it has to be obliterated for our convenience."

"Convenience?" Zyfete's face contorted with outrage. "You arrogant piece of shit!"

Tchicaya said wearily, "If you want to save people's homes, you have greater obstacles than me to overcome. Go and comfort your friend, or go and work on your model. I'm not going to trade insults with you."

"Don't you think it's insult enough that you come here and announce your intention to interfere, if we ever look like we might be on the verge of succeeding?"

He shook his head. "The Rindler was built by a coalition with no agenda beyond studying the novo-vacuum. The individual members all had their personal goals, but this was meant to be a platform for neutral observation, not a launching pad for any kind of intervention."

They'd reached the walkway. Tchicaya kept his eyes cast down, though he knew it made him look ashamed.

Zyfete said, "The bodiless I can understand: what lies outside their Qusps is irrelevant to them, so long as they can keep the same algorithms ticking over. But you've felt the wind. You've smelled the soil. You know exactly what we have to lose. How can you despise everything that gave birth to you?"

Tchicaya turned to face her, angered by her bullying but determined to remain civil. He said, "I don't despise anything, and as I've said, if it's possible, I'll fight to preserve all the same things as you. But if all we're going to do with our precious embodiment is cling to a few warm, familiar places for the next ten billion years, we might as well lock ourselves into perfect scapes of those planets and throw away the key to the outside world."

Zyfete replied coldly, "If you think a marriage has grown too stale and cozy, I suppose you'd step in and stave one partner's head in?"

Tchicaya stopped walking and held up his hands. "You've made yourself very clear. Will you leave me in peace now?"

Zyfete faced him in silence, as if she'd run out of venom and would have been happy to depart at precisely this moment, if only he hadn't asked her. After a delay long enough to preclude the misconception that she might be doing his bidding, she turned around and strode back along the walkway. Tchicaya stood and watched her, surprised at how shaken he was. He'd never concealed his views from the people he'd lived among - apart from keeping his mouth politely shut in the presence of anyone in genuine distress - and over the decades he'd had to develop a thick hide. But the closer he'd come to the source of the upheaval, the harder he had found it to believe that he was witnessing an unmitigated tragedy, like the floods and famines of old. On Pachner, where the sorrow and the turmoil had been at their most intense, he'd also felt most vindicated. Because beneath all the grief and fear, the undercurrent of excitement had been undeniable.

If Zyfete's attack had stung him, though, it was mostly through the things she hadn't said. Just being here meant that she had already left her own home behind, already tasted that amalgam of liberation and loss. Like Tchicaya, she had paid once, and no one was going to tell her that the price had not been high enough.

Tchicaya took a shower to wash off his vacuum suit, then lay on his bed, listening to music, brooding. He didn't want to spend every waking moment on the Rindler questioning his position, but nor did he wish to grow impervious to doubt. He didn't want to lose sight of the possibility that he had chosen the wrong side.

If the Preservationists did achieve their goal, the possibilities offered by the novo-vacuum need not be lost forever. Whatever was learned in the process of destroying it might open up the prospect of re-creating it, in a safer, more controlled fashion. In a few tens of millennia, there could be a whole new universe on their doorstep again, but this time it would pose no threat to anyone. No one would be forced from their homes. No one would be made to choose between exile and adaptation.

And in a few tens of millennia, how much tighter would the deadening spiral of familiarity have wound itself? If the nine-thousand-year history of Zapata was too precious to lose, after ninety thousand years every tradition, every grain of sand on every inhabited planet, would be positively sanctified.

Still, those who believed they were being smothered could always flee, as he'd fled Turaev. Those who were happy sleepwalking into eternity could stay. He had no right to force this cusp on anyone.

He didn't have the right, but he didn't have the power either, nor did he aspire to it. He was only here to state an unpopular case, and see if anyone could be swayed. If he believed that the novo-vacuum offered the greatest wealth of opportunities the species had faced since leaving Earth, what else would it be but cowardice and dishonesty if he failed to argue against its destruction?

The cabin was beginning to feel less spacious by the minute. He left it and made his way around the ship, heading for the garden. He still felt jittery on the walkways, but his confidence was slowly improving.

The garden was almost deserted. He found a bench that faced away from the border, offering a view he could take in without vertigo. The reel of the blue polar stars was slow enough to be soothing, and with the foliage to break up their perfect arcs the whole sight seemed less mechanical.

The Doppler shift was a novelty to him, but the motion of the stars was familiar. The night sky on Turaev had looked just like this, during a mild Slowdown. The only thing missing was the sun, rising and setting with each turn.

He'd stood by the crib that would prepare his body for storage, and his mind for transmission. It had asked him to state his wishes on the eventual recycling of this, his birth flesh. His father had pleaded gently, "We could still wait for you. For a thousand years, if that's what you need. Say the word, and it will happen. You don't have to lose anything."

Someone passing glanced his way, curious at the sight of an unfamiliar passenger. Their Mediators interacted, and the stranger requested an introduction. Tchicaya hadn't asked not to be interrupted, and he allowed the exchange of information to proceed. Protocols were established, translators verified, mutually acceptable behavior delineated. There were no local customs to defer to, here, so their Mediators virtually flipped a coin to decide the manner in which they should greet each other.

"I don't believe we've met. My name's Sophus."

Tchicaya stood and gave his own name, and they touched each other lightly on the left shoulder. "I've only been here a day," he explained. "It's my first time off-planet; I'm still adjusting."

"Do you mind if I join you? I'm waiting for someone, and this is the nicest spot to do it."

"You'd be welcome."

They sat on the bench. Tchicaya asked, "Who are you waiting for?"

"Someone who'll usurp your present role as most junior arrival. In fact, technically, I suppose she's already done that, but she's not yet in a state to show herself and claim the position."

Tchicaya smiled at the memory of his own appearance in the crib. "Two arrivals in as many days?" That wouldn't have been so strange if someone had been following him from Pachner, but he hadn't come across anyone there who'd shared his travel plans. "They'll be running out of bodies if this keeps up. We'll have to squeeze the ex-acorporeals right into the ship's processors."

Sophus frowned, mock-reprovingly. "Hey, no discrimination, please! It's up to them to volunteer, not us to suggest it."

"The way they offered to share those cabins, to make room for new arrivals?"

Sophus nodded, apparently amused by the gesture. Tchicaya felt a twinge of unease, unsure whether he had just endeared himself to Sophus with some remarks that had been taken as evidence of bigotry, or whether he was just being hypersensitive. He wondered how long it would take Sophus to quiz him about his allegiance; either the answer had spread through the grapevine already, or Sophus was polite enough to make small talk for a while, and see if he could extract the information indirectly.

"Actually, we'll start some new bodies growing soon," Sophus explained. "We were expecting a rush about now - give or take a decade. People will want to be here, it's what the models predicted."

Tchicaya was puzzled. "What, because of Zapata?"

Sophus shook his head. "It's far too late to save Zapata. Maybe not literally, but most people are realistic enough not to think that they can turn back the tide at the very last moment. Look a bit further down the track. A century, a century and a half."

"Ah." In the right company, Tchicaya might have made a joke of the prospect Sophus was raising, but it wasn't the kind of casual blasphemy he'd try out on a stranger. And the truth was, he did feel genuine sorrow, in some ways deeper than his feelings about Turaev's eventual demise. Like the uprooting of some much-loved, long-sedentary ancestor through whom a scattered family remained in touch, the exodus of Earth's people, and the destruction of its soil, would scar the hearts of even the most cosmopolitan travelers.

"There's still talk of moving it," Sophus said casually. "Pushing a white dwarf into the solar system, to carry it away. Sirius B is the obvious candidate." Tchicaya blinked at him, incredulous. "It wouldn't be impossible," Sophus insisted. "When you dump matter on a white dwarf, it undergoes tidal compression heating. If you do it in the right way, a significant amount squirts off in jets. If you arrange for asymmetric jets, and if you have enough mass to play with, you can achieve a modest net acceleration. Then you get the Earth into orbit around the star; the acceleration displaces the orbit, but it can still be bound."

"But to get Sirius B up to half the speed of light - "

Sophus raised a hand. "I know, I know! You'd have to gather so much reaction mass, and move all of it so swiftly into place, the damage would rival Mimosa. To wreak that kind of havoc just to put the whole ball of rock into exile as an unbroken whole would be like saving New York from the floods by blasting it all the way to Io. The only sane response is to work on designing an effective sandbag, while being prepared to give up gracefully and watch the place sink if that proves to be impossible."

"Yeah." If Tchicaya remembered the story correctly, though, while New York hadn't quite ended up on Io, gracefully watching the place sink would be putting things charitably. Hadn't some famous statue ended up in Paris, and various bridges and buildings gone to scattered theme parks?

Sophus attended briefly to an internal perception. "My colleague is on the brink of emerging. Would you like to meet her?"

"I'd be delighted." They rose together and headed for the stairs. On the walkway, Tchicaya forced himself to keep pace with Sophus, as if no one would make allowances for his lack of experience now that he'd ceased to be literally the rawest recruit.

"Where's she come from?"

"You mean, directly?"

"Yeah. I was on Pachner, and no one else there was talking about traveling to the Rindler. Maybe I just didn't bump into her - "

Sophus shook his head. "She's been in transit almost a century, standard time."

That was a long journey. Though it cost you more lost years in total to travel by an indirect route, breaking up the trip with as many stops as possible eased the sense of alienation. Whatever faction she supported, she had to be serious about the cause.

Tchicaya pictured a map of the region. "She's come from Chaitin?"

"Right."

"But she wasn't born there?"

"No. You know, you'll be able to ask her for her life's history directly, in a couple of minutes."

"Sorry." Maybe it was absurd to be so curious about the newcomer when he still knew next to nothing about the Rindler's other passengers, but Yann's gloomy summary, and his own limited experience, had already made him long for someone who'd shake up the status quo.

As they crossed the observation deck, the door to the recovery room opened. Tchicaya smiled in recognition at the newcomer's posture: loose-limbed and confident after the kinesthetic retuning, seizing up for a moment at the sight of the border.

Then he recognized something more, and his own body turned to stone again.

He didn't need to check her signature; she hadn't changed her appearance since their paths had last crossed. In fact, she hadn't changed in four thousand years, since the day they'd first parted.

Tchicaya broke into a run, blind to everything around him, calling out her name.

"Mariama!"

She turned at the sound. He could see that she was shocked, and then uncertain how to respond. He halted, not wanting to embarrass her. It had been twelve hundred years since they'd set eyes on each other, and he had no idea what she'd make of his presence.

Mariama held out her hands, and he ran forward to grip them in his own. They whirled around, laughing, surefooted on the polished floor, leaning back into their own centrifugal force, moving ever faster, until Tchicaya's arms ached and his wrists burned and his vision blurred. But he would not be the one to stop moving, and he would not be the one to let go.

Something unseen stung Tchicaya's hand, a vibration like a tuning fork held against the bone. He turned and stared at the empty space beside him, and a dark blur shivered into solidity.

"Quickly! Give your Exoself this code."

No sooner had the data passed between their Mediators than Tchicaya wished he'd rejected it. He felt as if he'd been tricked into catching something incriminatory thrown his way, the reflex action triggered by the object in flight turning out to have been the wrong response entirely.

"I can't!"

Mariama said, "No one will ever know. They're like statues. You'll be invisible."

Tchicaya's heart pounded. He glanced at the door, and caught himself straining his ears for footsteps, though he knew there'd be nothing to hear. Could she have really walked through the house undetected, marching right past his parents in that scandalous state?

"Our Exoselves scan for danger," he protested. "If anything happens at ordinary speed - "

"Did your Exoself detect me?"

"I don't know. It might have."

"Did it signal you? Did it bring you out of Slowdown?"

"No." He wasn't an adult, though. Who knew how differently theirs were programmed?

"We'll stay clear of them," Mariama explained. "I'm not doing this to pick their pockets. If we're not a threat to anyone, we won't trigger any alarms."

Tchicaya stared at her, torn. He had never feared his parents, but he basked in their approval. It only took the faintest shadow of disappointment on his father's face to make him ache with unhappiness. His parents were good people; valuing their high opinion was not just childish narcissism. If he did well in their eyes, he would be respected by everyone. Mariama was only Mariama: a law unto herself.

She inclined her head. "Please, Tchicaya. It's fun doing this, but I'm lonely without you."

"How long have you been out of Slowdown?"

Mariama averted her eyes. "A week."

That hurt. How lonely could she be, if it had taken her a week to miss him?

She put a hand over her mouth and mumbled, "Or two."

Tchicaya reached out to grab her arm, and she danced back and vanished from sight. He froze for a second, then rushed for the door, and stood with his back pressed against it.

He searched the room with his eyes, knowing that it was pointless looking for her if she did not want to be seen. Shadows slid across the walls and floor with hypnotic regularity. Lighting panels in the ceiling came on at night, and softened the changes at dusk and dawn, but even when he looked away from the window the diurnal cycle was obvious, everywhere.

Another week had passed, while he stood there. She could not still be in the room with him; even if she was able to go that long without food and water, she would have gone mad from boredom.

She reappeared in front of him like a trembling reflection in a pan of water, jolted into turbulence but quickly stilled.

"How did you get in?" he demanded.

She pointed a thumb at the window. "The same way I left."

"You're wearing my clothes!"

Mariama grinned. "They fit me nicely. And I'm teaching them lots of new tricks." She ran a hand down one sleeve and erased the old pattern, supplanting it with golden starbursts on black.

Tchicaya knew she was goading him, hoping to prod him into giving chase. She'd handed him the key; he didn't need anything more in order to pursue her. If he gave in and joined her now, at least he'd be spared an elaborate game of hide-and-seek.

He said, "Two weeks." That sounded more than generous, and the risk of his parents noticing his absence would be microscopic.

"We'll see."

Tchicaya shook his head. "I want you to agree to it. Two weeks, then we both come back."

Mariama chewed her lower lip. "I'm not going to make a promise I might not be able to keep." Then she read his face, and relented slightly. "All right! Barring exceptional circumstances, we'll come back in two weeks."

Tchicaya hesitated, but he knew that this was the closest thing to a guarantee he could hope to extract from her.

She held out a hand to him, smiling slightly. Then she silently mouthed the word Now.

Their Mediators were smart enough to synchronize the process without needing to be told. Tchicaya sent the code to his Exoself, and the two of them dropped out of Slowdown together. Switching the metabolic modes of cells throughout his body, and reconfiguring all the higher-level systems responsible for maintaining posture, breathing, circulation, and digestion took nearly fifteen minutes. The time passed imperceptibly, though, since his Qusp only resumed its normal rate once his body had completed the shift.

The light in his room had frozen into a late-winter's afternoon. He could hear a breeze moving through the trees beside the house, a different sound entirely to the throb of barometric pressure changes to which he'd grown accustomed. They were only six civil days into the Slowdown, but the new rhythms had seeped into his mind more rapidly than they'd had any right to, as if abetted by some process that his Exoself had neglected to retard.

Mariama tugged on his hand, pulling him toward the door. "Come on!" Her expression made a joke of it, but she couldn't disguise the note of genuine impatience. They were like lightning now, their least purposeful meanderings a dazzling feat in everyone else's eyes, but that still wasn't fast enough.

"Not that way." He gestured at the window.

Mariama said accusingly, "You're afraid to walk past them."

"Of course." Tchicaya gazed back at her calmly. It was perfectly reasonable not to want to be discovered, and however skillful she was at manipulating him, he wasn't going to be made ashamed of every last instinct of his own. "It's safer to use the window. So we'll use the window."

Mariama managed to look both amused and martyred, but she didn't argue. Tchicaya climbed out, then she followed him, carefully pulling the hinged pane closed behind her. He was puzzled for a moment; no one was going to notice an open window in the short time they'd be gone. But in two weeks, the night frosts would have left an indelible mark on some of his more fragile possessions.

As they crossed the garden, he said, "Don't you go home to sleep?"

"No. I've set up camp in the power station. All my food's there." She turned to face him, and Tchicaya was sure she was on the verge of demanding that he go back to the house to pilfer some supplies of his own, but then she said, "You can share it. I've got plenty."

The bright afternoon was eerily quiet, though Tchicaya doubted that he would have been unsettled if he'd heard no other voices for a minute, or an hour, on an ordinary day. As they stepped onto the road, he spotted two other pedestrians in the distance. During Slowdown, his Exoself had not only reprogrammed his own gait, it had tweaked his expectations of other people's appearance: moving with both feet constantly on the ground, positioning the arms to maximize stability, had looked as normal as it had felt. With his old notions of bodily dynamics restored, the pedestrians appeared, not merely frozen, but cowed and timid, as if they expected an earthquake at any moment.

He looked back at his house, quickly lowering his eyes from the windows to inspect the garden. Wind and rain could shift soil and pebbles into unwanted places on a time scale of decades, but the plants were engineered to herd those unruly elements; he'd watched the process with his own eyes. Out in the fields, the crops would be tending themselves, collectively arranging whatever changes they needed in irrigation and drainage, glorying in the strange seasons of unharvested bounty.

Tchicaya said, "How did you find the code?" It was the first Slowdown for both of them; she couldn't have stored it on a previous occasion.

Mariama replied casually, "It's not a big secret. It's not buried deep, or encrypted. Don't you ever examine your Exoself? Take apart the software?"

Tchicaya shrugged. He'd never even dream of tinkering with things on that level: his Exoself, his Mediator. Next thing you were probing the working of your own Qusp, dissecting your own mind. He said, "I only take things apart if I can survive not putting them back together."

"I'm not stupid. I make backups."

They'd reached the park. Four giant hexapods huddled motionless in a corner. The decorative robots consisted of nothing but six coiled legs, arranged as three pairs that met at right angles in the center. If they'd been endowed with even the mildest form of sentience, they would have gone insane from the lack of stimulation, but they were little more than pattern-recognizers on springs.

Mariama ran up to them and clapped her hands. The nearest one stirred sluggishly, shifting its center of mass and wobbling on the tripod of the three legs currently touching the ground. She started dancing back and forth, encouraging it, and it began to tumble for her.

Tchicaya watched, laughing, biting back an admonition: someone would notice that they'd moved, and know that the Slowdown had been violated. He doubted that the hexapods had memories, but there was machinery everywhere, monitoring the streets, guarding the town against unlikely dangers. The fact that they hadn't woken anyone didn't prove that they wouldn't be found out in the end.

Mariama weaved between the robots. "Aren't you going to help me?"

"Help you do what?" She'd managed to get all four of them moving simultaneously, without his aid. Tchicaya hadn't played with them since he was an infant, but he'd never been able to hold the attention of more than one at a time.

"Make them collide."

"They won't do that."

"I want to get their legs tangled together. I don't think they understand that that can happen."

"You're a real sadist," he protested. "Why do you want to confuse them?"

Mariama rolled her eyes. "It can't hurt them. Nothing can."

"It's not them I'm worried about. It's the fact that you enjoy it."

She kept her eyes on him without breaking step. "It's just an experiment. It's not malicious. Why do you always have to be such a prig?"

Tchicaya felt a surge of anger, but he fought it down and replied pleasantly, "All right, I'll help you. Tell me what to do." He caught the flicker of disappointment in her eyes before she smiled and started issuing detailed instructions.

The hexapods were primitive, but their self-and-environment model was more reliable than Mariama had imagined. After fifteen minutes trying to trick them into tying their legs into knots, she finally gave up. Tchicaya collapsed on the grass, breathless, and she joined him.

He stared up into the sky. It had grown pale already, almost colorless. It had been summer when the Slowdown began; he'd forgotten how short the winter days were.

Mariama said, "Has anyone you know even heard of Erdal?"

"No."

She snorted, her expectations confirmed. "He probably lives on the other side of the planet."

"So? Do you want half the planet to go into Slowdown, and the other half not?" Everyone on Turaev was connected somehow. While Erdal traveled, the whole world would wait for him, together. It was either that, or they broke into a thousand shards.

Mariama turned to face him. "You know why they do it, don't you?"

It was a rhetorical question. People always had an ulterior motive, and Tchicaya had always been taken in by their explanations. He squirmed like an eager child and asked with mock excitement, "No, tell me!"

Mariama shot him a poisonous look, but refused to be sidetracked. "Guilt. Cosmic apron strings. Do you think poor Erdal would dare not come home, with nine million people holding their breath for him?"

Tchicaya knew better than to dispute this claim directly; instead, he countered, "What's so bad about Slowdown? It doesn't hurt anyone."

Mariama was venomous. "While every other civilized planet is flowering into something new, we do nothing and go nowhere, ten thousand times more ponderously than before."

"Lots of other planets do Slowdown."

"Not civilized ones."

Tchicaya fell silent. A faint star had appeared directly above him, even before the sun had fully set.

He said, "So you'll leave one day? For good?" The question produced an odd, tight sensation in his windpipe. He'd never lost synch with anyone; he couldn't imagine that kind of unbridgeable separation.

"No."

He turned to her, surprised. She said, "I plan to whip the whole planet into life, instead. Anything less would just be selfish, wouldn't it?"

The machinery inside the power station was robust and intelligent enough to defend itself, and to safeguard any visitors, without the need for high fences or locked doors. Tchicaya remembered the place as being noisier the last time he'd explored it, but Slowdown had reduced the flow of waste from the town to an inaudible trickle. Energy was extracted from the waste by an enzyme-driven electrochemical process that he was yet to study in detail; fortunately, some of the energy ended up as heat, and even the diminished output was enough to make the building habitable at night. Mariama had made a nest of blankets right up against the coolant pipes that led to the radiator fins on the roof.

Tchicaya sniffed the air cautiously, but there was no trace of the usual offensive odor, maybe because there was not only less sewage passing through, but the undiminished runoff from the fields was diluting it. There was a strange, boiled-vegetable smell to the place, but it was nothing he couldn't tolerate.

Mariama had stockpiled cans of food, self-heating rations of the kind people took into the untouched, frozen lands to the south. It must have taken her a while to build up the collection without attracting suspicion. She handed him a can, and he pressed the tab to start it heating.

"How long were you planning this?" he asked.

"A bit more than a year."

"That's before I even knew Erdal would be traveling."

"Me too. I just wanted to be prepared, whenever it happened."

Tchicaya was impressed, and a little daunted. It was one thing to watch the sun and the stars racing around the sky, and think: what if I could be as fast as them? Plotting to break out of Slowdown before she'd even experienced it required an entirely different line of thought.

"What were you doing? Before you came to my house?"

She shrugged. "Just exploring. Messing about. Being careful not to wake the drones."

Tchicaya felt his face harden at this contemptuous phrase, but then he wondered how much allowance to make for the fact that she was always striving to provoke him. The calculations became so difficult at times, it drove him mad. He wanted the two of them to be straightforward with each other, but he doubted that would ever be her style. And he didn't want her to be different, he didn't want her to change.

He opened the can and hunched over his meal, unsure what his face was betraying.

After they'd eaten, they switched off the lamp and lay beneath the blankets, huddled together. Tchicaya was self-conscious at first, as if the contented glow he felt at the warmth of her body against his was at risk of turning into something more complicated, but he knew that it was still physically impossible for anything sexual to happen between them. The prospect of that guarantee eventually failing disturbed him, but it couldn't vanish overnight.

Mariama said, "Two weeks isn't long enough. You need to walk out of your room a centimeter taller: just enough to make your parents feel something is wrong, without being able to put their finger on it."

"Go to sleep."

"Or learn something you didn't know. Amaze them with your erudition."

"Now you're just mocking me." Tchicaya kissed the back of her head. He immediately wished he hadn't done it, and he waited, tensed, for some kind of rebuke. Or worse, some attempt to move further along a path on which he'd never meant to set foot.

But Mariama lay motionless in the darkness, and after a while he began to wonder if she'd even noticed. Her hair was thick at the back, and his lips had barely brushed a few loose strands.

In Tchicaya's view, the town's effective desertion didn't render it more interesting, and the freedom to wander the streets and fields at any hour was less appealing now, in winter, than in the ordinary summers when it was barely curtailed by parental authority anyway. Tchicaya thought of suggesting that they drop back into Slowdown and reemerge when the weather was warmer, but he was afraid of compromising their original deal. If he didn't stick to the letter of it, he could forget about holding Mariama to her word.

Mariama wanted to catch a train to Hardy, further if possible, preferably circumnavigating the entire continent. In one weird concession to practicality, the trains moved at their ordinary speed, whisking commuters to their destinations in an eye blink. Understandably, though, departures were rare, and on examining the schedules it turned out that they could not have traveled anywhere and back in less than ten years.

Tchicaya did his best to keep Mariama distracted, terrified that she might harbor a yearning for sabotage that went beyond playground equipment. She'd know it was futile to hope to succeed in damaging any of the town's infrastructure, but he could picture her delight at sirens wailing and people shuddering into motion around her. This image might have been unfair, but there was no point asking her for assurances; at best, that would only offend her, and at worst it might tempt her to act out his fears. So he tried to go along with any suggestions she made that weren't completely outlandish, but only after putting up enough resistance to keep her from becoming too bored, or too suspicious of his compliance.

On their tenth night out of Slowdown, Tchicaya was woken by lukewarm fluid dripping onto his face. He opened his eyes in the pitch blackness, and rashly poked his tongue out to sample the fluid. It was water, but it had a complicated, slightly metallic taint. He pictured a crack in the ceiling, the heat from the radiator fins above them on the roof melting the surrounding frost.

He slid out from the blankets without waking Mariama, and groped for the lamp. When he held it up, a faint liquid sheen was visible snaking down one thick coolant pipe, collecting in drops at a right-angled bend above the cushion where his head had lain.

Mariama stirred, then shielded her eyes. "What is it?"

"Just some water from the roof. We might have to shift." He moved the lamp about, hunting for leaks along the other pipes. Then something different caught his eye, a flash of iridescent colors at the very top of the pipe that had proved to be the original culprit. "Is that oil?" Why would there be oil leaking from the roof? As far as Tchicaya knew, the plant's few moving parts were all inside the building, and they'd all be molecularly smooth if they made physical contact with each other at all. Maybe flakes of ice could catch the light like that. But what could make them thin and flat enough?

There was sure to be a simple answer, but the puzzle gnawed at him. It was cold, and part of him wanted nothing more than to curl up beneath the blankets again - but what was the point of achieving a state in which no one could tell him to stop worrying and leave it till morning, if he didn't take advantage of his freedom to act on his curiosity immediately?

He said, "I'm going up on the roof."

Mariama blinked at him in the lamplight, apparently at a loss for words.

Tchicaya put on his shoes and walked outside, taking the lamp with him.

He circled the building twice, before settling on a sturdylooking drainpipe. The lamp was attached to a chain; he hung it around his neck, like a pendant worn backward, and gripped the drainpipe between his forearms and knees. There were no handholds, and the frosted surface was slippery. The first time he found himself sliding back down, he panicked and almost let go, but the friction from the polymer surface was never enough to really hurt him. After ending up back on the ground twice, he found that if he tightened his grip the instant he began to slip, he could bring himself to a halt in a fraction of a second, and retain most of his hard-won altitude.

He reached the roof with his limbs numb and his chest soaked in icy perspiration. He crouched on the sloped tiles, flapping his arms vigorously to try to restore the circulation, until he realized that this was driving him slowly backward toward the sevenmeter drop behind him. If he did real damage to his birth flesh, there'd be no prospect of concealing it from his parents. And to take on a new body at the age of twelve would make him a laughingstock for centuries.

He rose up on his haunches and waddled across the roof, as wary of gravity now as if he'd been back in Slowdown. He had no idea whether he was heading in the right direction; the dark shapes looming ahead of him might have been anything. He stopped to work the lamp around from his back to a more useful position, and noticed a long gash along the inside of his right leg, wet with blood. Something had cut him as he'd slipped along the drainpipe, but the wound wasn't painful, so it couldn't be too deep.

Up close, the radiator fins were massive, each as wide as his outstretched arms. He ambled around the structure, shining the lamp into the angled gaps between the fins, hunting for the source of the leak.

Mariama called out to him, "What have you found?" She was outside, on the ground somewhere.

"Nothing, yet."

"Do you want me to come up?"

"Suit yourself." He felt a twinge of guilt at the way that would sound, but it was hardly an expression of lofty disdain by the standards she'd set. This was the first thing he'd done since he'd joined her that wasn't part of some complicated strategy to please her, or confound her. He had to be indifferent to her, just this once, or he'd go mad.

When the lamplight finally returned the rainbow sheen he'd glimpsed from inside the building, it was unmistakable. An irregular, glistening patch of some filmy substance covered half the fin. Tchicaya approached, and touched it with a fingertip. The substance was slightly sticky, and the film clung to his finger for a fraction of a millimeter as he pulled away. When it parted from his skin he could feel it snap back elastically, rather than tearing like something viscous and treacly. He held his finger up for inspection; the skin was unstained, and when he rubbed it against his thumb there was no moisture or slickness at all. This wasn't any kind of oil he'd seen before, and it definitely wasn't ice.

He held the lamp closer to the surface, hunting for some sign of a damaged coolant channel. This had to be the residue left behind by a leak, though why the coolant would contain some sticky impurity was beyond him. Antifreeze? He was shivering with cold, but he was in a stubborn frame of mind.

A small hole appeared in the film at the center of the circle of lamplight, and grew before his eyes. He held the lamp as still as he could; once the boundary of the film had retreated into the penumbra cast by the lamp's housing, the hole stopped growing.

Tchicaya moved the lamp to another spot. The same thing happened: the lamplight seemed to melt the film away. But the beam carried no heat whatsoever. Was it driving some kind of photochemical reaction?

He turned back to the original rent in the film. It had shrunk to half the size it had grown to when he moved the lamp away. He made a hole in the film in a third location, then took the lamp back to inspect the second hole. It was closing up, too.

Tchicaya stepped out from the gap between the fins and sat huddled on the roof tiles, his teeth chattering. Maybe the light broke up whatever molecules the film was made from, while the chemical process that had formed it in the first place rebuilt it when he took the light away. Some mixtures of simple chemicals could behave in a complicated fashion. He had no right to start summoning up phrases from his biology lessons, like negative phototropism.

His arms were shaking. Mariama had been silent since their last exchange; she had probably gone back to bed.

He rose to his feet, and scrupulously searched the other parts of the radiator, but it was only one side of one fin that bore any visible trace of the film.

He took a knife from his pocket, opened it, and scraped it over the film. The surface appeared unchanged, but when he lifted the knife there was a waxy residue visible along the edge of the blade.

He walked around the structure, counting the fins as he went, orienting himself with the stars. He closed his eyes and pictured the arc the sun would make as it crossed the sky; it was an easier task now than it would have been before he'd sat for a year in the front room of his house and watched the ribbon of fire shift with the seasons. He stepped between two of the fins and dislodged whatever had adhered to the knife onto the clean surface of the radiator.

He looked up at the sky again. A million stars, a million dead worlds. Only four planets had ever held anything different. His hunch was sure to be disproved, but the prospect only made him smile. There were some things so large and outlandish that you could only wish for them with your tongue in your cheek, and to be disappointed when they failed to appear would be like throwing a tantrum and cursing the world because the sun failed to rise at your beck and call.

He made his way to the edge of the roof, his breath frosting in front of him.

As he was climbing down the drainpipe, his leg began to throb. His body had managed to close the wound, and now it was warning him not to break the temporary seal of collagen it had woven across the gap in his skin. As he adjusted his legs to shift the pressure away from the cut, Tchicaya made a decision: he wanted to remember this night, he wanted it to leave a mark. He instructed his Exoself never to permit the cells of his skin to grow back in their normal pattern across the wound. For the first time, he would let the world scar him.

"Why do we need to borrow your parents' ladder?"

Tchicaya waved Mariama back from the toolshed. "I'm hoping it won't trigger any alarms. If I tried to borrow someone else's, that might look like I was stealing." He didn't want her taking part in the act, though. That the house had permitted her to enter uninvited, and even borrow his clothes without his permission, proved that it was prepared to show some tolerance toward his friends. His parents had never been obsessed with safeguarding their possessions, so it was not surprising that they hadn't programmed any paranoid, hair-trigger responses. He didn't want to push his luck, though.

When he emerged from the shed, Mariama said, "Yes, but what do we need it for? What's so interesting, up on the roof?"

Tchicaya swung the ladder toward her, making her jump back. "Probably nothing." He had planned to show her the film on the coolant pipes inside the building when she woke that morning, but by daylight the sight had been so drab and uninspiring that he'd changed his mind; she'd probably looked herself, and seen nothing but a mild discoloration. She'd laugh at his naiveté when he finally described his experiment, but he didn't care. "We'll find out tonight."

Mariama was puzzled. "What's to stop me going up there before nightfall?"

Tchicaya tightened his grip on the ladder, but even if he could keep it from her, she wouldn't need it.

He said, "Nothing. I'm asking you to wait, that's all."

This answer seemed to please her. She smiled back at him sunnily.

"Then I'll wait."

The ladder couldn't stretch to the full height of the roof, and Tchicaya had to argue with it before it would extend itself at all.

"It's not safe," the ladder wailed.

"I've already been up there once, without any help from you," he protested. He showed it his new pink scar. "I'll climb up the drainpipe again if I have to. You can either make this as safe as possible, or you can stay on the ground and be completely useless."

The ladder gave in. Tchicaya gripped the bottom end firmly while a wave of deformation swept along the length of the device. As the side rails stretched, material was redistributed into new rungs. In its final shape, paper-thin, the ladder was still a meter too short to touch the edge of the roof, but it would bring it within reach.

Mariama said, "After you."

Tchicaya had planned to follow her up, so he'd have a chance to catch her if she slipped, but he'd been assuming that she'd demand to go first anyway, so he had no argument prepared. He mounted the ladder and began to ascend. He didn't need to look down to know when she'd joined him; he could feel the structure vibrating with a second load.

If she did fall and injure herself, she could retreat at will into the painless world of her Qusp. An accident would mean discovery and shame, but no great suffering. Yet Tchicaya's hands shook at the thought of it, and he could not imagine feeling differently. The structure of his mind had been passed down with only a few small modifications from the original human form, shaped by evolution in the Age of Death, leaving him with the choice between embracing its impulses in all their absurdity - like ancient figures of speech whose literal meaning bore no resemblance to anything people still did - or struggling to invent a whole new vocabulary to replace them. If you cared about someone, what could replace the sick feeling of the misery you'd feel if they came to harm? The bodiless, he knew, had found their own, varied answers, but the idea that he might one day do the same made him giddy.

He peered down.

Mariama said, "What?"

"Nothing."

The long climb was far easier than it had been the night before, but Tchicaya found the act of reaching back to grab hold of the gutter a lot more disconcerting while perched on the top rung of the ladder than when he'd gripped the drainpipe firmly with his legs. He hoisted himself up and clambered onto the roof, then moved away from the edge quickly so he wouldn't be in Mariama's way. Seconds later, she was beside him.

"We should have used ropes, and grappling hooks," she said. "Like they do on mountains."

"I never thought of that," Tchicaya admitted.

"I was joking."

"It might have been fun, though." It might have been safer.

"Are you going to let me in on the big secret now?"

Tchicaya feigned indifference. "I did warn you: there's probably nothing to see." He aimed the lamp's beam across the roof, but deliberately kept it low. "This way."

They crossed the tiles together in silence. When they reached the radiator, Tchicaya showed her the patch of iridescent film he'd discovered the night before.

Mariama examined it. Tchicaya had half-expected her to identify the substance immediately, puncturing his fantasy with a far simpler explanation, but she was as baffled as he was. When he showed her how the film responded to the lamplight, she said, "Is that why you thought there'd be nothing here? You expected the sunlight to destroy it?"

"No. This surface ought to be in the shade all day."

"It would still get some light from the sky, though."

"That's true," he conceded. "But if it was there last night, it either had to be able to survive that much indirect sunlight, or it had to have formed after sunset, at least once. So why wouldn't it be here again?"

Mariama nodded patiently. "All right. So what were you warning me not to expect?"

Tchicaya's throat tightened. "I scraped some off, and put it on another fin. One that should have been about equally shaded. To see if it would..." He couldn't say the word.

"To see if it would grow?"

He nodded stupidly.

Mariama whooped with delight. "Where!" She clutched at the lamp, but when he held on to it she didn't fight him for it. Instead, she took hold of his arm and said, "Will you show me? Please?"

They stumbled around the radiator, helping each other stay balanced. Tchicaya told himself he didn't care what they found; when there turned out to be nothing, they could laugh at his grandiose delusions together.

"This is the one." He aimed the lamp into the wedge-shaped space between the fins, but he couldn't hold it still. "Do you see anything?"

Mariama put an arm around him, steadying his whole body to steady the lamp.

There was a patch of the film in front of them, an oval about the size of his hand, at exactly the height where he would have scraped the knife clean.

Mariama took the lamp, and knelt to inspect the patch more closely. It began to shrink immediately; she pulled the light away.

"This wasn't here last night?"

"No."

"So it must be a new..." She struggled for the right word.

"Colony? Do you think that's what it is?"

"I don't know."

She turned to him. "But it is alive? It has to be!"

Tchicaya was silent for a moment. He'd thought the result would settle the issue, but now he was having second thoughts. The evidence was still too flimsy to support the extraordinary conclusion. "There are chemicals that do some strange things," he said. "I'm not sure what this proves."

Mariama rose to her feet. "We have to wake someone, and show them. Right now."

Tchicaya was horrified. "But then they'll know what we did.

They'll know we broke Slowdown."

"No one will care. Don't you know how rare this is?"

He nodded. "But you promised me - "

Mariama laughed. "We're not going to be in trouble! This is a thousand times more important!"

Apart from Earth itself, native life had only been found on three worlds. Simple and microbial, but in each case unique. Every biosystem used different chemistry, different methods of gathering energy, different structural units, different ways of storing and transmitting information. On the crassest, most pragmatic level, this knowledge might be of little value: technology had long ago surpassed nature's ability to do all of these things efficiently. But each rare glimpse at a separate accident of biogenesis cast light on the nature and prospects of life. The roof of this building would become the most talked-about location for a hundred light-years.

Tchicaya said, "What if it's something we brought ourselves? That wouldn't be much of a discovery."

"Such as what? Nothing we brought can mutate freely: every cell in every crop, every cell in our bodies, has fifty different suicide enzymes that kill off the lineage at the first genetic error. This could no more be ours than if they found some strange machine out in the ice that nobody owned up to making."

Tchicaya was growing tired of trying to keep his balance on the sloping roof; he sat down, his back slumped against the fin. It was lukewarm, body temperature. Once Slowdown ended, it would be hotter than the boiling point of water. So which extreme did the native life favor? Had it grown here before the Slowdown, and then managed to cling on in the relative cool? Or had it blown out of the icy wastes and only colonized the radiator once the Slowdown had rendered this tiny niche benign?

Mariama sat beside him. "We'll have to leave," she said.

"Can't that wait until morning?"

"I don't mean us, now. We'll have to leave Turaev. They'll evacuate the planet. We'll all have to go somewhere else." She smiled, and added with a kind of mock jealousy, "I always wanted to be the one to shake this place out of its stupor. But it looks as if you've beaten me to it."

Tchicaya sat motionless, scowling slightly. The words refused to sink in. He knew that she was right: it was a universal principle, accepted by every space-faring culture. In each of the other three cases, the planet in question had been strictly quarantined and left to its own fate. Only one of those worlds had been settled, though. Native life was supposed to have been ruled out, long before the colonists' first spores were launched. However microscopic, and however sparsely distributed, it should have left some detectable chemical signature in the atmosphere.

Tears stung his eyes. In his euphoria, he'd never thought beyond the unlikely confirmation that his own world, his own town, held the fourth known example of extraterrestrial life. He could have lived down the shame of this childish escapade, half-excused by that serendipitous discovery. But he'd been more than disobedient, more than disrespectful of the customs that bound the people of Turaev together. He'd destroyed their whole world.

He didn't want to weep in front of Mariama, so he stammered out an incoherent stream of words instead. Everything he'd planned, everything he'd pictured for the future, had just turned to ashes. He might have traveled one day, like Erdal, but he would never have left his friends and family behind, never lost synch. Fifty-nine generations had made this planet their home; he could never belong anywhere else. Now it would all be torn away from him. And nine million people would suffer the same fate.

When he stopped to catch his breath, Mariama said soothingly, "Everything here can be moved! Every building, every field. You could wake up on New Turaev, a thousand light-years away, and if you didn't check the stars you'd never know."

Tchicaya replied fiercely, "You know it will never happen like that! Five minutes ago, you were crowing about it!" He wiped his eyes, struggling not to turn his anger against her. He'd always understood what she wanted; he had no right to blame her for that. But any reassurance she offered him was hollow.

Mariama fell silent. Tchicaya buried his head in his hands. There was no escape for him: only adults had the right to shut down their Qusp, to choose extinction. If he threw himself from the roof and broke his spine, if he doused himself in oil and set himself alight, it would only make him more contemptible.

Mariama put an arm around his shoulders. "On how many worlds," she said, "do you think they've found life?"

"You know the answer. Three, since Earth."

"I don't know that. There might have been ten. There might have been hundreds."

Tchicaya's skin crawled. He looked up and searched her eyes in the starlight, wondering if she was testing him. What she was proposing now was infinitely worse than anything they'd done so far.

She said, "If you believe it will hurt so many people, so badly, then I'll listen to you." Tears were trickling down his cheeks again; she wiped them away with the back of her hand. "I'll trust you."

Tchicaya looked away. She had the power to incinerate everything around her, the power to break through every stifling absurdity she'd railed against from the day they'd met. When they'd spoken of the future, it was all she had ever talked about: finding a way to force the world to change. Now she could gut the planet with its own stupid rules, and nothing would ever be the same.

Unless he asked her to stay her hand.

Tchicaya slept through the end of Erdal's Slowdown, and woke from deep dreams, refreshed but disoriented. He lay in bed, listening to the wind, thinking over what had happened in the last two hundred and seventy-two years.

Erdal had traveled to Gupta, a hundred and thirty-six light-years away, and stayed for ten days. When he rose from the crib, back in his birth flesh, he would find that ten days had passed on Turaev, too. He would be the one bearing news, eagerly describing his travels to his family and friends. He would not be a stranger to them, greeted with an incomprehensible litany of change.

The whole planet had waited for him. What else should they have done? Turaev's sun would burn for four billion years. How much greed and impatience would it take to begrudge the wait, to cast someone aside for the sake of a few centuries?