Tchicaya"s Mediator woke him. It had just received a messenger from Branco, and judged it urgent enough to break him out of sleep.

He let the messenger run. He didn"t want to close his eyes and risk drifting off again as he watched, so he hallucinated Branco standing in the darkened cabin beside the bed.

"This had better be important," Tchicaya said.

"I"m very sorry to disturb you," the messenger whispered. It was much more polite than Branco himself. "But this is something you"ll want to hear. I"m only telling a handful of people. People I trust."

"I"m flattered."

The messenger gave him a look that suggested it was not immune to irony. "Someone has been trying to take control of the ship. I don"t know who. The proximate, physical source of the attack was a spare communications link for external instruments, sitting in a storage area that hundreds of people have had access to.

"There was no chance of the attack succeeding. Whoever did this must be awfully naive about some of the technology they"re dealing with." Tchicaya felt a frisson of recognition; hadn"t Tarek imagined that Yann could "corrupt" the ship"s network, just by running on one of its Qusps? "But it suggests a combination of foolishness and desperation that might not stop with this. So I"m telling a few reasonably level-headed members of both factions: you"d better find out who these idiots are, and keep them from going any further. Set your own houses in order, or you might all find yourselves walking the airlock."

The messenger bowed, and vanished. Tchicaya blinked into the darkness. "Walking the airlock" was a quaint way of putting it, but he didn"t think Branco was bluffing. If factional squabbling reached the point where the Rindler itself was at risk, Tchicaya didn"t doubt that the ship"s builders would evict the squatters, one way or another.

He woke Rasmah, and shared the news.

"Why didn"t Branco tell me?" she complained. "Why am I not trustworthy?"

"Don"t take it personally. He probably just thought it would give the message more gravitas if it trickled through, instead of going straight to everyone."

She leaned over and kissed him. "I was joking, actually, but thanks for the reassurance." She groaned. "Oh, here we go."

"What?"

"Yann wants to talk to us." She hesitated. "And Suljan. And Umrao."

"We need to get together. We need to organize a meeting." Tchicaya picked up his pillow and put it over his face. "I can"t believe I just said that."

Rasmah laughed and patted his arm. "We do have to discuss this. But you won"t need to get out of bed."

Rasmah had her Mediator arrange the protocols, then she invited Tchicaya into a virtual Blue Room. His viewpoint drifted across the floor, toward a table where Rasmah, Yann, Suljan, Hayashi, and Umrao were seated. He knew he was visible to the others as an icon, and he could alter his gaze and make gestures at will, but he had no real sense of being embodied in the scape; he still felt himself lying motionless on the bed.

Suljan said, "Any ideas, Tchicaya?"

"Who could be so foolish as to try this? I thought of Tarek, but that doesn"t add up. Unless he"s involved in some elaborate bluff."

Hayashi shook her head. "Not Tarek. I heard that the Preservationists split down the line on the vote, but he was definitely on the side of the moratorium."

"You"re saying it was close?"

"Closer than I"d expected," she replied. "Almost forty percent against. Mostly new arrivals."

"Forty percent." Tchicaya had being fervently hoping that Murasaki and Santos were rare extremists. And it was still possible that they were; you didn"t have to be sanguine about genocide to have voted against the moratorium, merely skeptical that destroying the far side would entail anything of the kind. Perhaps some of the newcomers had found the unfamiliar physics so bewildering that they"d decided they simply couldn"t trust the evidence for the signaling layer, even with their own experts confirming it.

Yann said, "We shouldn"t rule out some hothead in our own camp. Just because we"ve achieved the moratorium, that doesn"t guarantee that we"ll get everything else people want."

Suljan sighed. "That"s very even-handed of you, but given the timing, it doesn"t seem likely to me."

"It could have been a setup, though," Umrao suggested. "Someone who hoped their tampering would be detected, and get us all thrown off the Rindler - which would put back any prospect of the Preservationists unleashing their Planck worms by several centuries."

Rasmah said, "At the cost of every last trace of goodwill and cooperation between the factions. At the cost of everything we"d learn in the year of the moratorium."

"The neutrals would continue to do research," Umrao replied.

Tchicaya said, "Getting thrown off the ship is no good for either side. It must have been someone who really did think they could succeed."

"Succeed at what, exactly?" Hayashi asked. "They wanted control of the ship, in order to do what?"

Bhandari appeared suddenly, standing beside the table. "I hate to interrupt, but if any of you here are interested in reality..." He held up a framed image showing a view of one of the Rindler's tethers. Six people were clinging to the cable near the top of one of the modules, slowly ascending toward the hub. Strapped to the backs of two of the climbers were bulky, box-shaped objects that looked as if they might have been built from the same modules as the instrumentation packages for the border experiments. Tchicaya didn"t recognize the silver-suited figures, but he asked the ship to match their facial geometry with its manifest of occupants. The six were Murasaki, Santos, and four other newcomers, all of whom had arrived more or less together from Pfaff.

Rasmah vanished from the scape, and Tchicaya felt her shaking him by the shoulders. "Get up!"

He complied, momentarily disoriented.

"What?" he asked. "What do you think they"re doing?"

"I don"t know, but we have to be prepared for the worst." Rasmah grabbed her can of suit spray and hurriedly coated him. "Now spray me. Quickly!"

Tchicaya did as she"d asked. "The worst? What are you expecting?"

"They"re headed for the engines, aren"t they? Can you think of a benign explanation for that? I want you to go straight to the shuttle."

"Why? You"re not turning protective on me, are you? I"ve backed up last night. Even if we die here, I"m not going to forget you."

Rasmah smiled, and shook her head. "Sorry to be unromantic, but I"m thinking about more than us. If these people manage to remove the Rindler, someone has to be around to protect the far side. No one else I trust is any closer to the shuttle."

Tchicaya started pulling on his clothes. "Then come with me."

"No. Until we know what"s happening, it"s better we split up. They might have done something to the shuttle, it might be a lost cause. Better that only one of us goes there, while the other tries to stop them doing anything at the hub."

Tchicaya felt a surge of resentment, but this argument made sense, and she wasn"t ordering him around for the sake of it. They had to move quickly, and it was pointless quibbling over who did what.

He asked the ship for a view of the shuttle. It was still docked in the usual place, and it appeared to be intact, though that hardly ruled out sabotage.

"You"re going up after them?" he said.

"If the builders trust me enough to let me out there."

"How did those six get outside? Assuming Branco didn"t toss them out."

Rasmah finished dressing. "They"re on the tether that holds the module with the instrumentation workshop. They must have been pretending to be working on some sensor that needed to operate in vacuum." She glanced around the cabin with an air of finality, as if she was putting her memories of the place in order.

Tchicaya ached to hold her, but he didn"t want to make it harder for them to part. As they stepped out into the corridor, he said, "If this all goes wrong, where will we meet?"

"My closest backup is on Pfaff. If it stops getting reassurance signals from here, that"s the one that will wake."

"Mine too."

"That"s where we"ll meet, then." She smiled. "But let"s see if we can achieve a swifter reunion."

They"d reached the stairs. Tchicaya said, "Be careful."

"Of all the things I came here to be, that was never on the list." She took his face in her hands, and touched her forehead to his. Tchicaya listened to her breathing. She was excited, and afraid, and she hadn"t followed her own advice about adrenaline. She didn"t want to be calm, for this.

Then she released him, turned, and bolted up the stairs without another word.

As Tchicaya took the stairs down toward the walkway, he asked the ship to show him the instrumentation workshop. There was some kind of half-assembled sensor sitting on the main platform, open to space, but he could see no obvious clues as to what Murasaki and the others intended. What did they think they were going to do at the hub? Hot-wire the engines and drive the Rindler away? That was never going to happen. It would be a simpler task than taking control of the whole ship, but not by much. Assuming they were being wildly optimistic, though, what good would it do their cause if they succeeded? Whisking everyone away from the border would only delay the work of both sides.

As Tchicaya panned around the workshop, he saw a dark, powdery stain on the floor, by the airlock.

"What"s that?" he asked the ship.

"Blood."

The whole workshop was always in vacuum, and it would take much more than a minor act of carelessness to cut yourself through a suit.

"Can you show me when it was spilt?"

The ship showed him recorded vision from fifteen minutes before. As Santos stepped through the airlock, blood dripped from his fingers to the floor. His suit was only just beginning to silver against the cold; Tchicaya could still see his face. One nostril was full of red and black clots, only contained by the membrance of the suit, and the lid of one half-closed eye was encrusted with blood. He looked as if he"d been smacked in the face with an iron bar. Had he been in some kind of struggle with the others? It was bizarre.

On the walkway, Tchicaya saw Kadir coming toward him. They approached each other warily. Kadir spread his arms in a protestation of innocence. "I"m not with these lunatics! We disown them!"

"Do you know what this is all about?"

"I know that they opposed the moratorium, but I don"t have a clue what they think this will get them. Birago"s joined them now, but he"s the only one I really knew. The others were never very communicative. They claimed they were travelers like you, but they were never at ease with anyone but each other. Whatever the faults of travelers, if you express an opinion they find unusual, they tend not to stop in midconversation and stare at you as if you"d sprouted wings."

"Where"s Birago?" Tchicaya asked.

"Last I heard, he was standing guard at the entrance to the workshop, trying to stop anyone getting through and going after them."

"But he won"t say what they want? There"s no threat, no conditions they"re trying to bargain for?"

Kadir said, "I think this has gone beyond bargaining."

"Is the Right Hand secure? Could they have used it, done something with it, without the rest of you knowing?"

Kadir shrugged. "The records say it"s done nothing for days. But Birago helped build it. I don"t know what he was capable of doing."

They parted. As Tchicaya reached the end of the walkway, Rasmah spoke in his head. "The builders let me out. I"m up on the cable." Even through an unvocalized radio channel, her Mediator made her voice as expressive as ever; she sounded both nervous and exhilarated, as if she almost welcomed the chase. "I"m a fair way behind our mutineers, but I think I"m gaining on them."

"You"re outnumbered, and they"re completely deranged." Tchicaya told her about Santos"s appearance.

"Suljan and Hayashi are heading for another tether. They begged Branco to let them out before, but he fobbed them off, he said there was no need. I guess the builders changed their mind."

Tchicaya jogged through the bottom level of his own accommodation module. He was still three modules away from the shuttle. "So they thought they could deal with it, but then they realized they couldn"t?" He struggled to make sense of this. The tethers clearly weren"t made of anything smart enough to impede the rebels, or dispose of them directly; the insides of the modules were endlessly reconfigurable, but it probably never occurred to the builders that these cables would require any property but tensile strength. "What were they pinning their hopes on?" he mused. "Picking them off with debris-clearance laser? You"d think that would either be technically feasible, or not."

"Maybe they had some last-minute moral qualms."

"These people are either trying to hijack the ship, or to destroy it, and they"re free to send backups wherever they like. Their memories are in their own hands. I doubt Branco would have had any scruples about vaporizing them, if it were possible."

Rasmah said, "He might have been outvoted."

Tchicaya asked the ship to show him an image of her. The lone figure was only about five or six meters up the kilometer-long cable, but she was ascending rapidly: gripping the slender braid of monofilaments with her knees, reaching up, dragging her body another arm"s-length higher. At least at the hub she"d have a negligible velocity; if she ended up floating, he"d have plenty of time to reach her in the shuttle.

Tchicaya said, "Let me see through your eyes."

"Why?"

"Just for a moment. Please."

Rasmah hesitated, then sent him the vision. She looked down at the shiny globe of the module beneath her, then up across the spoked wheel of the ship, toward the faint glint of her quarry on the tether a quarter of a turn away. On her right, the dazzling plain of the border was as serene and immutable as ever.

"I"m not afraid of heights," she said dryly. "Stop fretting about me." She cut off the image.

"I"m not," Tchicaya lied.

"I just spotted Suljan emerging. Look, I"m not on my own here. Just get to the shuttle! If there"s anything to tell you, I"ll call back."

"All right."

As his sense of her presence faded, Tchicaya broke into a run. He"d been wasting time trying to piece everything together; he didn"t need to know exactly what the rebels were planning. Rasmah"s logic was sound. He hated not being beside her, but she"d trusted him with another task, and he had to dedicate himself to it, unswervingly.

He raced past people in the corridors and on the walkways, without stopping to shout questions or exchange hypotheses. If there was solid information being passed around, it would reach him eventually, wherever he was. Within minutes, he was dripping with sweat; the ship"s bodies stayed reasonably fit by sheer biochemical fiat, but his own had been neither designed nor trained for speed. Refusing to be swayed by discomfort was easy, but there were limits that had nothing to do with pain.

Yann appeared suddenly, sprinting beside him. "Rasmah said you"re heading for the shuttle. How much free storage do you have in your Qusp?"

"Not enough for a passenger. I"m sorry."

Yann shook his head, amused. "I don"t need a ride. I"m entirely used to not having my Qusp on legs, and I"m not worried about getting my memories elsewhere. But if you"re stranded, you might need some assistance."

Tchicaya replied purely by radio, to save his breath. "That"s a good idea. But like I said, I don"t have storage for a second person."

"I didn"t expect you would," Yann said. "I"ve prepared a toolkit; it"s only a few exabytes, but it encompasses everything I know about the far side. Everything I"ve learned from Suljan, Umrao, and the others, and everything I"ve worked out for myself. Of course, all of this is useless if you don"t have access to the border, so I"m organizing a vote on ceding control of the Left Hand to you."

Tchicaya didn"t reply. Yann said, "You probably don"t want all this riding on your shoulders, but believe me, we"re doing our best to avoid that."

Tchicaya said, "What can they do up there?"

"Don"t worry about that. Just get to the shuttle, and move away as fast as you can. We"ll call you back once it"s safe."

"Assuming the rebels don"t steal the shuttle first." He checked the view; it was still in place.

Yann said, "They can"t steal it; the builders have disabled it. Branco has agreed to release it once you"re onboard. Now stop arguing, and take the toolkit."

Tchicaya instructed his Mediator to accept the package. Yann added cheerfully, "Let"s hope you don"t need it."

As Yann"s icon vanished, Tchicaya swerved to avoid a startled pedestrian, who stared at him as if he"d gone mad. No one he"d encountered since leaving Rasmah had been in much of a hurry, and the closer he came to the shuttle, the more people seemed to be heading in the opposite direction: away from the Rindler's sole lifeboat. Some planet-bound part of him found this surreal; there were few inhabited worlds where it would have been entirely pointless to abandon a burning ship in the middle of the ocean. Even in cultures where the loss of flesh was taken lightly, there were usually volunteers willing to make the effort to rescue endangered people who felt differently. Perhaps there were some crowded circumplanetary orbits where the shipwrecked could expect to be plucked bodily from the vacuum, but fleeing the Rindler as anything but a signal would have been raising optimism to new heights.

As he crossed the final walkway, Tchicaya asked the ship for a view of the entrance to the shuttle. There was no one visible, no one standing guard. He was on the verge of asking for a sequence of images covering the entire remainder of his journey when he spotted a group of people with his own eyes, ahead of him on the walkway. Four of them hung back, while a fifth approached, carrying a long metal bar.

Tchicaya slowed, then halted. The rebel kept walking toward him, briskly and purposefully. Tchicaya"s Mediator could detect no signature, but the ship put a name to the face: Selman.

Tchicaya caught his breath, then called out amiably, "Talk to me. Tell me what you want." Selman continued toward him in silence. His face was even more damaged than Santos"s; there was a ridge of scarlet running along the side of his nose, and a massive edema around the eye socket. His four companions were similarly marked. If this was a sign of internal disputation, the whole group should have torn itself to shreds weeks ago.

Suddenly, Tchicaya understood. Selman wasn"t withholding his signature as a gesture of hostility, or in an attempt to conceal his identity. He had no signature, and no Mediator to send it. He had no Exoself. He had no Qusp. The rebels had improvised some kind of crude surgical tool, and plucked each other"s digital brains out.

Tchicaya said, "Talk to me, and I"ll find the right translator! We still have all the old languages." He wasn"t expecting to be understood, but he could still provoke a response. Assuming Selman hadn"t lost the power of speech entirely. Tchicaya didn"t know how much neural tissue a Homo sapiens needed in order to be fully functional. Bodies like the Rindler's had plenty of neurons in reserve, since the precise delegation of tasks between the digital components and the central nervous system varied widely from culture to culture. He suspected that even this reserve was less than the size of a complete ancestral brain, but a careful redesign might still have packed everything in.

With ten or twelve meters remaining between them, Selman stopped and spoke. Tchicaya couldn"t even parse the speech into separate words; to his untrained ear it sounded like a continuous flow. This was the first time in his life that he"d begun a conversation with a stranger without the ground being prepared in advance, without two Mediators conspiring to bridge the gap. A moment after the utterance was complete, though, he recalled the sounds and understood them.

"Turn around and go back, or I"ll beat you to a pulp."

Tchicaya replied in the same tongue, or what he hoped was near enough to be comprehensible. His Mediator had traced Selman"s words back to a language from twenty-third century Earth, but it was compensating on the fly for the kind of variations that could arise over millennia in an isolated population of the original speakers.

"As opposed to what? Turn around and go back, and fry with the ship?"

Selman said, "If the builders are willing to take the ship away from the border, no one has to fry."

Tchicaya shrugged. "Flee or fry, it"s all the same to us. The only thing at stake is access to the border, so every choice that would put an end to that is equivalent. You can fly us all the way to Earth, or you can crack our heads open one by one, but don"t expect to get any more cooperation for one alternative than another."

Selman said, "Spare yourself the pain, then. Or the mess, if pain is beneath you." He stepped forward, swinging the bar. Tchicaya had no knowledge of martial arts; he delegated the problem to his Exoself, and watched the interaction as a detached observer until he was standing with one foot on the back of Selman"s neck, and holding the bar himself.

"That wasn"t even you, you bloodless worm!" Selman hissed.

"Oh, you noticed?" The other four were approaching; two of them were hefting large potted plants, a choice of weapon more alarming for its strangeness than its bulk. "None of this was necessary," Tchicaya said. "Whatever grievance you had, we would have given you a hearing."

"We gave our arguments peacefully," Selman replied. "Hours ago."

"What arguments? Evolutionary imperatives, and winning back territory? We"re the ones who"ve lost two thousand systems. You haven"t lost a single ship."

"So you expected us to sit back and do nothing? While you betrayed your own species, and wiped out the last vestiges of humanity?"

Tchicaya was still struggling to come to terms with the rebels' origins. To pass as ordinary travelers at all, they must have translated themselves into versions that ran on their Qusps, as well as their Trojan-horse brains. Lying in wait, impotently watching their other halves act, must have been a deeply unpleasant experience. The neural versions would not have been able to follow much, if any, of what was spoken around them - even when the words passed through their own lips - so the Qusp versions would have had to brief them later, whispering in private in their native tongue. Coming prepared to survive their own preemptive digital lobotomies had been prescient, though. Tchicaya was almost certain now that the builders possessed halt switches for all the ship"s Qusps; that would have been the method they"d hoped to use against the rebels heading for the hub, before changing their mind and sending Rasmah and the others in pursuit.

The other four anachronauts stood before Tchicaya. One of them, Christa, said, "Let him go, and back away."

"Or what? You"ll beat me to death with your rhododendron?" Tchicaya asked the ship, "What is that? Is it one of yours?"

"Originally, but it"s been tweaked."

"Into something dangerous?"

"There"s nothing obviously harmful being expressed in the leaves or stalk."

"And the roots?"

"I have no way of knowing about the roots."

Christa repeated, "Let him go, and back away. This is your last chance."

Tchicaya asked his Exoself if it could relieve both rebels of their pots without spilling the contents. It could make no promises.

He said, "I have nothing to gain by retreating."

Christa glanced down at Selman, her mask of grim resolve melting for an instant. She was stranded in a deranged, alien world, and she believed she was about to die.

Tchicaya said, "We can - "

She raised the pot to her shoulder, and started to shake the plant free. Tchicaya told his Exoself to keep as much as it could from falling; he sprang forward, grabbed the stalk, and forced the plant back into its container. As Christa toppled backward, his Exoself had him reach out with his other hand and secure the pot around the roots.

As he did this, in the corner of his eye he saw another anachronaut swinging the second plant by its stalk. The roots were already free of the pot, and the soil around them was falling away. Between the gnarled gray fingers of the roots were dozens of swollen white nodules. Tchicaya told his Exoself to prevent the nodules from coming into contact with anything solid. It knew how fast he was capable of moving, and how fast he needed to be. The task, it declared, was impossible.

The anachronaut slammed the roots of the plant down on the floor.

Tchicaya lost everything but his sense of motion. He was deaf and blind, falling, waiting for an impact. He"d been thrown into the air, so he had to come back down to the ground eventually. That made sense, didn"t it?

The impact never came, but his vision was restored in an instant. His suit had turned fully opaque to protect his eyes; now it had decided that it was safe for him to see again. He was outside the Rindler, falling away from it. He could see the damaged walkway narrowing into two hourglass waists on either side of the ruptured section, pinching it off, stopping the flow of air. A skein of filaments was already beginning to crisscross the wound.

He looked around for the anachronauts. He spotted one in the distance, silhouetted against the borderlight, sharing the velocity he"d acquired from the Rindler's spin but separated from him by the force of the blast. The limbs were fixed at unnatural angles; he was looking at a corpse. All the ships' bodies could switch modes and cope without oxygen, but between the explosion and the exposure to vacuum there"d been no prospect of anyone surviving unprotected. The rebels had had more time than anyone else to think about putting on suits before endangering themselves, but they"d apparently decided not to bother. That was either willful martyrdom, or the expectation that, whatever happened, no one was going to be left alive to come and rescue them.

Branco spoke. "Are you all right?"

"I think so." If his suit had been damaged at all by the blast, it had since repaired itself, and his Exoself reported nothing more than bruising to his body.

"I"ll send the shuttle after you."

Tchicaya said, "Thanks." He waited, watching numbly as the necklace of the ship continued to recede. He was tumbling slowly around an axis that almost coincided with the direction of his motion; the Rindler never vanished from sight, but the horizon between the border and the stars wheeled in front of him.

Branco said, "Plan A might not be possible. They"ve glued the shuttle"s release bolts in place."

Tchicaya pondered this, dreamily amused for a moment. The sheer strangeness of his situation had induced a sense of detachment; it was a struggle to think his way back into events on the ship.

"What"s happening at the hub?"

"We reviewed what the climbers were doing earlier, in the instrumentation bay," Branco replied. "They were building a particle detector, with some powerful superconducting magnets. Which are now part of the devices they have with them."

"The fuel must be shielded, though? Against stray magnetic fields?" The antimatter portion was kept in a purely magnetic container; that had to be robust.

"Do you have any idea how many orders of magnitude difference there is between stray interstellar fields and the strongest artificial ones?"

Tchicaya took this question to be rhetorical. "How close are Rasmah and the others?" He didn"t want to look for himself; he just wanted Branco to give him the good news.

"They"re close. But the rebels are already at the hub, setting things up."

"And you believe they might be capable of spilling the fuel?"

"We can"t rule that out. It will depend how good their device is. If they"re smart, and if they have time, they could pump energy into two different flows that the containment fields couldn"t restrain simultaneously."

Tchicaya said nothing. He closed his eyes. He"d screwed up, he"d let his guard down with the anachronauts, but Rasmah was unshakable. She"d stop them, if she got the chance.

Branco said, "We"re now seeing flows developing in the fuel." His voice betrayed no hint of panic. After the loss of the Scribe, he"d told Tchicaya that he"d been through local death seven hundred and ninety-six times, but even if he was immune to existential qualms, the prospect of losing contact with the border had to be painful. "Listen to me carefully. There"s no way we"re going to get the shuttle free in the next few minutes, but we could use the debris-clearance laser to burn through the tether that"s holding the module to which the shuttle is docked."

"What good would that do? The whole module is swarming with rebels."

"There are five known rebels - who we"ve managed to contain by reconfiguring some walls - but there are also three other people. All three are declared Preservationists, but they might still be your allies. If I throw the module clear of the Rindler, and everyone else is lost, they might get the shuttle free. And if the Rindler survives, at least they"ll have a chance of getting back to us."

Tchicaya said, "Who are the three?"

"Alejandro, Wael, and Mariama," Branco replied. "I don"t know any of them well. But you"re the one who"d be left here with them, so you"d better decide whether that would be to your advantage or not."

The retreating ship was vanishing into the borderlight. Tchicaya didn"t want the power to gamble with anyone"s fate, but the rebels had left the builders with no choice but to juggle odious alternatives, and now Branco had dragged him into the same quagmire.

If the rebels were trying to destroy the Rindler, it was because they believed they had nothing more to do here, which meant that the Right Hand was already primed to scribe Planck worms without further intervention. Sparing everyone in the module wouldn"t put the far side in any greater danger, so he should err on the side of saving those people, in the hope that they"d help him fight the Planck worms. If he was left here alone, drifting off into the distance, he might be able to control the Left Hand remotely for a while, but without the shuttle he"d eventually lose radio contact.

The rebels could still be mistaken, though. The first attempt to create the Planck worms could fail. If anyone aligned with the rebels remained, they could work to rectify those early mistakes; they"d have decades to achieve their goal, virtually guaranteeing that the far side would be obliterated. So maybe it would be safer to be left alone, to do whatever he could in the time he had.

It all came down to whether or not one or more of those three people had been swayed by the rebels, as Birago had been swayed. Birago, who"d always seemed passionate but reasonable, and nowhere near as fanatical as Tarek.

Alejandro, Wael, and Mariama.

Branco said, "We"ve worked out the strategy the rebels are using. It"s not the best, but it is effective. If they"re not stopped, they"ll definitely spill the fuel."

Tchicaya said, "Cut it loose."

He stared at the horizon, watching for some glint from the laser in action, but that was futile. He couldn"t see any part of the ship anymore, and the portion of the tether that was glowing white hot would only be centimeters long.

"Branco?"

"Nearly there. It will take a few more seconds. Rasmah"s just reached the hub. She"s fighting with two of the rebels." Branco chuckled "Make that one."

Tchicaya"s spirits soared. He asked the ship to show him the struggle.

There was no response. He asked again.

On the horizon, a dazzling bead of violet light appeared, outsining the border. Then his suit shut off his vision.

When the first, paralyzing wave of despair had left him, Tchicaya tried to contact Mariama. Without success, but he"d steeled himself for that further small blow. He didn"t know which way the module had been flung, but with every minute that passed both of them were six kilometers further from the point where the Rindler had been, and it was possible that they were already too far apart for direct Mediator-to-Mediator contact. The module would have its own longer-range transceivers, but it was possible that they"d been damaged by the radiation from the Rindler's fireball.

He had to be patient. If Mariama had survived, she would find a way to contact him.

Belatedly, it occurred to him to try the Left Hand. It responded. The vote Yann had spoken of had gone through in time: the Left Hand not only acknowledged his signal, it was willing to take instructions from him.

He had his Mediator construct a virtual replica of the familiar Blue Room console, and he placed himself before it. He merged Yann"s toolkit with the interface, and summoned the first simple menu of possibilities. For several seconds, he was too afraid to do anything but stare at the screen. Then he scribed a probe that would enter the far side and return as quickly as possible.

Minutes later, the echo came back to him. The surface layer of the far side, at least, was unchanged, populated by exactly the same mix of vendeks as they"d seen with the first experiment.

He tried a deeper probe. The result was the same: nothing had changed.

Tchicaya left the scape. He watched the horizon hopefully, sifting through the possibilities. The rebels had chosen not to scribe the Planck worms before mounting their attack on the ship. Perhaps they"d feared that they"d encounter more determined resistance from their opponents, if the annihilation of the far side was already playing out right before their eyes. A premature assault on the border would also have weakened the position of the remaining Preservationists, if the mutiny had been crushed. In any case, the fact that they"d felt a need to destroy the Rindler implied that the rebels were not confident that the process would be unstoppable once it had begun.

If the rebels hadn"t arranged for the loss of the ship to trigger the event immediately, there had to be some kind of timer counting down. If Mariama had got the shuttle free, she might have headed straight for the Right Hand, to pluck it out of the equation completely. If Birago had successfully corrupted it, the Right Hand would not take orders from her, and it was certainly more able to look after itself than the Scribe had been, dodging far larger shifts in the border. But Tchicaya doubted that it was equipped to defend itself from a determined assailant. The shuttle had more powerful engines; if it came down to brute force, she could probably bulldoze the Right Hand straight into the border.

If she reached it in time.

And if she was willing.

Three and a half hours after the loss of the Rindler, the border was transformed. Tchicaya didn"t perceive anything approaching; he merely saw the expanse of white light replaced in an instant by an opalescent gray. He turned just in time to catch sight of the edge of the change as it vanished behind him.

The sphere of the border was so vast that the true geometrical horizon was a billion kilometers away, but to his unaided vision everything beyond about a million kilometers occupied a single line, too narrow to resolve. After replaying the event, his calculations could not rule out the possibility that the change had swept by at lightspeed. That would have made it literally impossible to see coming, and then the delayed evidence of the fleeing edge would have given the impression that it was traveling at half its true speed, crossing the million kilometers he could distinguish in about six seconds.

He checked with the Left Hand. Being closer to the border, its field of view was smaller than Tchicaya"s, but its instruments left his senses for dead. It had tracked the change he"d witnessed, and judged it to be moving at the speed of light.

Not roughly, not nearly, but, to the limits of measurement, precisely the speed of light. Which meant that the Planck worms could not be pursued, let alone stopped.

The battle was over. The far side was lost.

Tchicaya caught himself angrily. The ability to move across the border at lightspeed didn"t guarantee the power to penetrate the far side at the same rate. For all he knew, he"d just seen nothing more than a variation on Branco"s surface-pinning effect.

He told the Left Hand to scribe another probe.

It couldn"t. The border had retreated.

Retreated how far? The Left Hand couldn"t tell him. How do you measure the distance to a featureless, immaterial plane of light? Once the border had slipped out of range of the particle beam of the stylus, the Left Hand had lost the ability to summon forth any kind of echo. It had scattered a small cloud of electronic fireflies, moving at about ten meters a second, to see when they were extinguished. So far, they all remained intact. It was no use tracking the brightness of the borderlight; each square meter of the border would seem dimmer as it retreated, but that effect was canceled out precisely by the fact that any particular instrument you aimed at it, with some fixed angle of view, would be taking in light from a larger portion of the border the further away it was. And there was no Doppler shift to reveal the velocity of retreat: the far side was being pared away, not pushed away, and the new, gray borderlight was being emitted from a succession of different surfaces, not a single moving source that could act as a clock.

The Left Hand had detected a microscopic lowering of the horizon against the backdrop of stars, which did prove that the Planck worms had corroded the far side into vacuum hundreds of thousands of kilometers away. But the line of sight from the Left Hand to the new horizon still only penetrated twenty or so meters below the surface where the border would normally have been; the growing crater could be as shallow as that limit, or it could be a million times deeper.

Tchicaya waited. The fireflies could still wink out at any moment. The Left Hand"s engines weren"t powerful, and it carried only a small reserve of fuel, but it could adapt to a shift in the border"s velocity of a few meters per second.

After ten minutes, nothing had changed. The fireflies were still visible. The border was outracing them.

That did not mean that there was no hope left. But to move the Left Hand faster than the fireflies, to have any chance at all of catching the border, he would need the shuttle.

He was useless on his own, now. It all came down to three Preservationists, and whether or not the hint of life in the far side had been enough to change their minds.

Tchicaya woke his father with a tug of the hand.

"What is it?" His father squinted at him blearily, but then he smiled and put a finger to his lips. He climbed out of bed and scooped Tchicaya into his arms, then carried him back to his own room.

He put Tchicaya down on the bed and sat beside him.

"You can"t sleep?"

Tchicaya shook his head.

"Why? What"s wrong?"

Tchicaya didn"t need to have the truth coaxed out of him. "I don"t want to get older," he said. "I don"t want to change."

His father laughed. "Nine isn"t old. And nothing"s going to change tomorrow." It was his birthday in a few hour"s time.

"I know."

"Nothing"s going to change for you, for years."

Tchicaya felt a flicker of impatience. "I don"t mean my body. I"m not worried about that."

"What, then?"

"I"m going to live for a long time, aren"t I? Thousands of years?"

"Yes." His father reached down and stroked Tchicaya"s forehead. "You"re not worried about death? You know what it would take to kill a person. You"ll outlive the stars, if you want to."

Tchicaya said, "I know. But if I do...how will I know that I"m still me?"

He struggled to explain. He still felt he was the same person as he"d been when he was seven or eight, but he knew that the creature of his earliest momeries, of three or four, had been transformed inside his skin. That was all right, because an infant was a kind of half-made person who needed to be absorbed into something larger. He could even accept that in ten year"s time, some of his own feelings and attitudes would be different. "But it won"t stop, will it? It won"t ever stop."

"No," his father agreed.

"Then how will I know I"m changing in the right way? How will I know I haven"t turned into someone else?" Tchicaya shuddered. He felt less dread now that he wasn"t alone, but his father"s mere presence couldn"t banish this fear entirely, the way it had banished the terrors of his childhood. If a stranger could displace him, step by step over ten thousand years, the same thing would be happening to everyone. No one around him would be able to help, because they"d all be usurped in exactly the same way.

His father conjured up a globe of the planet and held it toward him, a luminous apparition painted over the gray shadows of the room. "Where are you, right now?"

Tchicaya turned the globe slightly with a gesture, then pointed to their town, Baake.

"Here"s puzzle for you," his father said. "Suppose I draw an arrow here, on the ground in front of you, and tell you it"s the most important thing there is." He marked the globe as he spoke. "Wherever you go, wherever you travel, you"ll need to find a way to take this arrow with you."

This was too easy. "I"d use a compass," Tchicaya said. "And if I didn"t have a compass, I"d use the stars. Wherever I went, I could always find the same bearing."

"You think that"s the best way to carry a direction with you? Reproducing its compass bearing?"

"Yes."

His father drew a small arrow on the globe, close to the north pole, pointing due north. Then he drew another on the opposite side of the pole, also pointing due north. The two arrows shared the same compass bearing, but anyone could see that they were pointing in opposite directions.

Tchicaya scowled. He wanted to claim that this was just a perverse exception to an otherwise reasonable rule, but he wasn"t sure that was the case.

"Forget about north and south," his father said. "Forget about the stars. This arrow is your only compass; there is nothing else to steer by. You must take it with you. Now tell me how."

Tchicaya stared at the globe. He drew a path leading away from Baake. How could he duplicate the arrow as he moved? "I"d draw another arrow, each time I took a step. The same as the one before."

His father smiled. "Good. But how would you make each new one the same?"

"I"d make it the same length. And I"d make it parallel."

"How would you do that?" his father persisted. "How would you know that the new arrow was parallel to the old one?"

Tchicaya was unsure. The globe was curved, its geometry was complicated. Maybe it would be simpler to start with a flat surface, and then work his way up to the harder case. He summoned a translucent plane and drew an arrow in black. On command, his Mediator could duplicate the object faithfully, anywhere else on the plane, but it was up to him to understand the rules.

He drew a second arrow and contemplated its relationship with the first. "They"re parallel. So if you join the two bases and the two tips, they make a parallelogram."

"Yes. But how do you know that they make a parallelogram?" His father reached over and skewed the second arrow. "You can tell that I"ve ruined it, just by looking, but what is it that you"re looking for when you see that?"

"The distances aren"t the same anymore." Tchicaya traced them with his finger. "From base to base and tip to tip, it"s different now. So to make the second arrow a copy of the first, I have to make sure that it"s the same length, and that its tip is as far away from the first one"s tip as the bases are from each other."

"All right, that"s true," his father agreed. "Now suppose I make things more difficult. Suppose I say you have no ruler, no tape measure. You can"t measure a distance along one line and duplicate it on another one."

Tchicaya laughed. "That"s too hard! It"s impossible, then!"

"Wait. You can do this: you can compare distances along the same line. If you go straight from A to B to C, you can know if B is exactly half the journey."

Tchicaya gazed at the arrows. There was no half journey here, there was no bisected line in a parallelogram.

"Keep looking," his father urged him. "Look at the things you haven"t even drawn yet."

That clue gave it away. "The diagonals?"

"Yes."

The diagonals of the parallelogram ran from the base of the first arrow to the tip of the second, and vice versa. And the diagonals divided each other in two.

They worked through the construction together, pinning down the details, making them precise. You could duplicate an arrow by drawing a line from its tip to the base you"d chosen for the second arrow, bisecting that line, then drawing a line from the base of the first arrow, passing through the midpoint and continuing on as far again. The far end of that second diagonal told you where the tip of the duplicate arrow would be.

Tchicaya regarded their handiwork with pleasure.

His father said, "Now, how do you do the same thing on a sphere?" He passed the globe over to Tchicaya.

"You just do the same thing. You draw the same lines."

"Straight lines? Curved lines?"

"Straight." Tchicaya caught himself. Straight lines, on a globe? "Great circles. Arcs of great circles." Given any two points on a sphere, you could find a plane that passed through both of them, and also through the center of the sphere. The arc of the equatorsized circle formed where the plane cut through the surface of the sphere gave the shortest distance between the two points.

"Yes." His father gestured at the path Tchicaya had drawn, snaking away from their town. "Go ahead and try it. See how it looks."

Tchicaya copied the arrow once, a small distance along the path, using the parallelogram construction with arcs of great circles for the diagonals. Then he had his Mediator repeat the process automatically, all the way to the end of the path.

"That"s it," Tchicaya marveled. "We"ve done it." A lattice of diagonals ran along the path, marking the way, carrying the arrow forward. No compass, no stars to steer by, but they"d found a way to copy the arrow faithfully from start to finish.

"It"s beautiful, isn"t it?" his father said. "This is called Schild"s ladder. All throughout geometry, all throughout physics, the same idea shows up in a thousand different guises. How do you carry something from here to there, and keep it the same? You move it step by step, keeping it parallel in the only way that makes sense. You climb Schild"s ladder."

Tchicaya didn"t ask if the prescription could be extended beyond physics; as an answer to his fears, it was only a metaphor. But it was a metaphor filled with hope. Even as he changed, he could watch himself closely, and judge whether he was skewing the arrow of his self.

"There"s one more thing you should see," his father said. He drew a second path on the globe, joining the same two points but following a different route. "Try it again."

"It will be the same," Tchicaya predicted confidently. "If you climb Schild"s ladder twice, it will copy the arrow the best way, both times." It was like being asked to add up a dozen numbers twice, grouping them in different ways. The answer had to be the same in the end.

"So try it again," his father insisted.

Tchicaya complied.

"I"ve made a mistake," he said. He erased the second ladder, and repeated the construction. Again, the second copy of the arrow at the end of the path failed to match the first.

"I don"t understand," Tchicaya complained. "What am I doing wrong?"

"Nothing," his father assured him. "This is what you should expect. There"s always a way to carry the arrow forward, but it depends on the path you take."

Tchicaya didn"t reply. He"d thought he"d been shown the way to safety, to persistence. Now it was dissolving into contradictions before his eyes.

His father said, "You"ll never stop changing, but that doesn"t mean you have to drift in the wind. Every day, you can take the person you"ve been, and the new things you"ve witnessed, and make your own, honest choice as to who you should become.

"Whatever happens, you can always be true to yourself. But don"t expect to end up with the same inner compass as anyone else. Not unless they started beside you, and climbed beside you every step of the way."

Tchicaya made the globe vanish. He said, "It"s late. I"d better go to sleep now."

"All right." His father stood as if to leave, but then he reached down and squeezed Tchicaya"s shoulder. "There"s nothing to be afraid of. You"ll never be a stranger, if you stay here with your family and friends. As long as we climb side by side, we"ll all change together."

"Tchicaya? Can you hear me?"

It was Mariama.

"Loud and clear," he said. "Are you all right?"

"That depends what you mean by me. My Qusp is fine. Parts of my Mediator got fried; I only have a short-range IR link left. My body"s not a pretty sight, but it"s recovering."

The signal was coming to him via the Left Hand; she"d freed the shuttle and gone there in person. The long-range transceivers in both the module and the shuttle must have suffered irreparable radiation damage, which said something about the likely state of her body.

"What about the others?"

"Wael and Alejandro received similar exposure. They helped me get the shuttle unglued, but they weren"t interested in sticking around, with no mod cons and such poor company. Birago"s body seemed to be in better shape than mine, but the builders halted his Qusp, so he"s as good as departed. When I left, the other rebels were all in a bad way; some of their bodies had reverted to undifferentiated goo, and even in the ones that were still intact and breathing, I"d be surprised if their minds have survived the repair process."

She was probably right; the bodies would make liberal use of apoptosis to kill off radiation-damaged cells, and there was no reason for them to treat neural tissue any differently.

Mariama said, "I went to the Right Hand first, but it had already scribed the Planck worms. It wasn"t pursuing the border down, but I gave it a nudge in the opposite direction, too fast for it to reverse. If we find some use for it, I could go and drag it back, but I"m hoping the Left Hand will be enough."

"It will have to be." Nothing they did to the Right Hand would render it trustworthy.

"Branco told me about the toolkit Yann gave you, while he was cutting us loose, but I didn"t have time to get a copy myself. The simplest thing might be if you send it to me now, before I go chasing the border."

"What?" Tchicaya stared at the red-shifted stars above the horizon, checking the view for any sign that he"d departed from reality and was hallucinating this entire encounter. "Why would that be simplest? You"re coming to get me, aren"t you?"

"That would be an awful waste of fuel. You don"t need to be here, physically."

Tchicaya was silent for a moment. She was right about the fuel, but he couldn"t accept what she was proposing.

"That"s not true," he said. "If I stay out here, I"m going to lose radio contact, eventually. From sheer distance in the long run, but if the border has taken on a complicated shape, I might lose my line of sight much sooner."

"Then give me the key to the Left Hand. With that, and the toolkit, I can manage everything." She sighed. "Don"t be precious about this. I don"t like the idea of leaving you to drift away, but there are more important things at stake here. The time and the fuel I used fetching you could make all the difference to the far side."

Tchicaya felt a flicker of temptation. He could wash his hands of everthing, and wake beside Rasmah on Pfaff. Mariama was being perfectly logical; time was against them, and apart from the secondhand skills that he could easily sign over to her, he was superfluous.

He wanted to trust her. Hadn"t she earned that? They"d had no end of differences, but she had always been honest with him. It seemed petty and mean-spirited to keep on doubting her.

The trouble was, he didn"t trust his own motives. Thinking the best of her would be the perfect excuse to absolve himself of all responsibility.

He said, "I"m not handing you anything. If you care so much about the far side, you"d better come and get me."

Mariama remained seated at the front of the shuttle as Tchicaya clambered out of the airlock. He nodded a greeting, and tried to smile. Her Exoself would be discouraging her from doing anything to interfere with her body"s healing, by means both gentler and more precise than a blanket of agony; extrapolating from the raw pain of the minor burns he"d willingly experienced as a child was absurd. Still, the sight of her weeping, blistered skin made his guts tighten.

He said, "Hitchhiking in space isn"t so bad. I"ve waited longer for a ride, on land."

Mariama replied through the IR link. "Try showing more flesh. That always works wonders."

On their way back to the Left Hand, Tchicaya received the first good news he"d heard since the moratorium vote. The horizon had stopped falling. The Left Hand was no longer seeing new stars creeping into view.

That in itself didn"t fix the depth of the lost region everywhere, but the particular geometry was suggestive. The new horizon was exactly where it would have been if the Planck worms had failed to penetrate the signaling layer, where the vendek population changed abruptly, a hundred kilometers into the far side.

As they approached the Left Hand, the news became even better. The fireflies had finally begun to vanish, and the timing of their deaths confirmed the best possible scenario: the border had retreated to the signaling layer, and no further.

Tchicaya was elated, but Mariama said, "Don"t assume this is the new status quo. Birago wasn"t exactly confiding in me toward the end, but if what he"s done here bears any resemblance to the work I was involved in with Tarek, the Planck worms won"t have given up at the first obstacle."

"Meaning what?"

"They"ll mutate. They"ll experiment. They"ll keep on varying themselves, until they find a way to break through."

"You knew how to do that? You had it all worked out?"

"No," she admitted. "But as soon as you showed us the vendeks themselves, they provided an awful lot of inspiration. Tarek and I didn"t pursue that, but don"t expect Birago to have passed up the opportunity."

They docked with the Left Hand, and carried it down to the point where the fireflies were disappearing.

Regaining alignment with the border took almost an hour, as a cycle of increasingly delicate adjustments brought the stylus into range. Once that was achieved, Tchicaya scribed a series of probes that would spread out laterally as well as moving straight in, improving their chances of gaining a comprehensive picture of the Planck worms. Unsurprisingly, now that the signaling layer was infected with Planck worms and exposed to vacuum, it was no longer vibrating, no longer tapping out primes. Tchicaya longed to discover the mechanism that had driven it, but he had to stay focused; trying to dissect the far-siders' ruined SETI equipment - if that was what it was - had to take second place to dealing with the plague the beacon had been unable to deter on its own.

As he launched the last probe, he turned to Mariama. "If you gave me all the details of the work you did with Tarek, there"d be no need for you to hang around."

She emitted a disgusted wheezing noise, the first real sound he"d heard her make. "Is that some kind of childish comeback, because I didn"t want to waste fuel on making you cozy?"

"No. But I"m the one who came to the Rindler to protect the far side. There"s no reason for you to keep crawling over broken glass for the sake of someone else"s agenda."

Mariama searched his face. "You really don"t trust me, do you?"

"To do what? To betray your own ideals? You always wanted to wipe this thing out."

"I never thought that would involve genocide."

"We"re still not certain that it would."

She sighed, bodily. "So you"re afraid that if we find a natural explanation for the signaling layer, my presence might suddenly become embarrassing?"

"Wouldn"t it?"

"I voted for the moratorium," she said. "I voted to do nothing but look for signs of life, for a full year. Whatever happens, I"ll honor that commitment."

Tchicaya experienced a twinge of shame, but he didn"t back off. He said, "Make up your mind. Are you here to protect the far side? Or are you here to relaunch the Planck worms in a year"s time, if the far side proves to be sterile?"

Mariama shook her head. "Why do I have to choose? If there are sentient creatures in there, they deserve our protection. If there"s nothing but an exotic ocean full of different kinds of Planck-scale algae, then the sooner it"s rendered safely back into vacuum, the better. Is that distinction really so hard to grasp? What did I ever do to get lumped in with the rebels, in your head? When"s the last time I displayed nineteenth-century morality?"

"Twenty-third."

"That just shows how little history you know. Most people who left Earth in that era did so precisely because they were out of step with contemporary mores. In this case, I"d say they were about four centuries behind the times."

Tchicaya looked away. Was she protesting too much? But she was just as entitled as he was to be contemptuous of the anachronauts' views. Being wise after the fact about the complexity of the far side, and the unwitting genocide the Preservationists might have committed, was like blaming the Mimosans for failing to anticipate the failure of the Sarumpaet rules.

The probes began returning. The Planck worms they revealed were dauntingly complex structures, at least as elaborate as the vendeks themselves. And Mariama had been right: they"d begun to mutate, to try out variations. The software counted thousands of strains.

Even if they were capable of adaptation, though, they were too simple to achieve it through anything but trial and error. Their designer had left them to fend for themselves, and in the end that would leave them as vulnerable as any other dumb pathogen.

Tchicaya addressed the toolkit, allowing Mariama to listen in. "Find a graph we can scribe that will wipe these things out - without moving deeper and damaging the native vendeks." As he spoke the words, this sounded like a breathtakingly optimistic request, but the Planck worms themselves had been seeded from a single point, so there was no reason why the antidote couldn"t be introduced the same way.

There was a perceptible delay while the toolkit explored the problem. "I don"t believe that"s possible," it declared. "The Planck worms are exploiting the ordinary vacuum behind them: they set up correlations across the border that cause the vendeks to decohere. I"m unable to find a method of attacking the Planck worms that wouldn"t also destroy the whole vendek population in which they"re immersed."

Mariama said, "What if the vendek population changes, deeper in?"

"Anything might be possible then, but until I know the details, there are no guarantees."

Tchicaya scribed probes to look deeper.

The second change swept the border as swiftly as the first. Through the windows of the shuttle, they saw the smooth gray plain transformed into a complex, striated pattern of dozens of bright hues. Tchicaya"s heart raced; it was like watching a pool of acid eat its way down through featureless rock, exposing thousands of delicately layered sediments.

Mariama said, "The border must be motionless again, or we"d see the pattern changing. So the Planck worms have hit more obstacles. We might have killed them off, if we"d burnt away this whole layer first."

"Including whatever it contained," Tchicaya countered. "We have no idea what might have been there."

Mariama replied flatly, "Whatever was there, it"s gone now anyway."

Tchicaya said nothing, but she was right. If he"d acted more swiftly, they might have cauterized the wound. If he was going to refuse to make decisions with imperfect knowledge, he might as well give up intervening and simply leave the far-siders to protect themselves.

The Left Hand had launched fresh fireflies immediately, but he wasn"t going to wait for them. He told the shuttle to follow them down, keeping just enough distance to be sure it could decelerate in time.

The new border lay some sixty kilometers down, but its altitude was no longer constant; the shuttle came to a halt in the middle of a sinuous valley. The borderlight around them revealed the striations they"d seen from afar to be just one level of structure: the bands were crossed with networks of fine, dark lines, super-imposed over shifting waves of increased luminosity. And this was just the naked-eye view of a ravaged landscape, exposed to the vacuum and thick with alien marauders. What the pristine depths contained on a xennometer scale, Tchicaya couldn"t begin to imagine, but between these macroscopic structures and the vendeks themselves, the opportunities for complex life were greater than ever.

While they waited for the stylus to realign itself, Mariama said, "Can I ask the toolkit something?"

Tchicaya nodded warily.

"How complex an algorithm could you inject into the far side?" she said.

The toolkit replied, "On what time scale? If you give me long enough, there are no limits."

"How long would it take to inject yourself?"

"Scribing all the data directly with the Left Hand? About a hundred thousand years."

Mariama laughed in infrared. "What about other ways of doing it? What"s the most efficient method that would be achievable with the hardware at our disposal?"

The toolkit fell silent, conducting an exhaustive search.

Tchicaya said, "What"s this about?"

"We"re blind up here," she replied. "All our time and effort is going into shuttling information back and forth across the border. Yann and the others have given you a lot of valuable knowledge, but the place where it needs to be applied is the far side."