The Planetary Government aircraft was a sleek silver flying wing with its own atomic reactor, feeding six engines buried in air-smoothed nacelles. Minla had already led Merlin down a spiral staircase into an observation cupola set under the thickest part of the wing. Now she touched a brushed-steel panel, causing armoured slats to whisk open in rapid sequence. Through the green-tinted blastproof glass they had an uninterrupted view of the surface rolling by underneath.

  The ocean carried no evidence of the war, but there was hardly any stretch of land that hadn't been touched in some fashion. Merlin saw the rubble-strewn remains of towns and cities, some with the hearts gouged out by kilometre-deep craters. He saw flooded harbours, beginning to be clawed back by the greedy fingers of the sea. He saw swathes of grey-brown land where nothing grew any more, and where only dead, petrified forests testified to the earlier presence of living things. Atomic weapons had been used in their thousands, by both sides. The Skylanders had been first, though, which was why the weapons had a special name on Lecythus. Because of the shape of the mushroom cloud that accompanied each burst, they called them Minla's Flowers.

  She pointed out the new cities that had been built since the ceasefire. They were depressing to behold: grids of utilitarian blocks, each skull-grey multi-storey building identical to the others. Spidery highways linked the settlements, but not once did Merlin see any evidence of traffic or commerce.

  'We're not building for posterity,' she said. 'None of those buildings have to last more than fifty years, and most of them will be empty long before that. By the time they start crumbling, there'll be no one alive on Lecythus.'

  'You're surely not thinking of taking everyone with you,' Merlin said.

  'Why not? It seemed unthinkable forty years ago. But so did atomic war, and the coming of a single world state. Anything's within our reach now. With social planning, we can organise matters such that the population shrinks to a tenth of its present size. No children will be allowed to be born in the last twenty years. And we'll begin moving people into the Space Dormitories long before that.'

  Merlin had seen the plans for the Dormitories, along with the other elements of Minla's evacuation programme. There was already a small space station in orbit around Lecythus, but it would be utterly dwarfed by the hundred Dormitories. The plans called for huge air-filled spheres, each of which would swallow one hundred thousand evacuees, giving a total in-orbit human presence of ten million people. Yet even as the Space Dormitories were being populated, work would be under way on the thousand Exodus Arks that would actually carry the evacuees out of the system. The Arks would be built in orbit, using materials extracted and refined from the moon's crust. Merlin had already indicated to Minla's experts that they could expect to find a certain useful isotope of helium in the topsoil of the moon, an isotope that would enable the Arks to be powered by nuclear fusion engines of an ancient and well-tested design.

  'Forced birth control, and mass evacuation,' he said, grimacing. 'That's going to take some tough policing. What if people don't go along with your programme?'

  'They'll go along,' Minla said.

  'Even if that means shooting a few, to make a point?' 'Millions have already died, Merlin. If it takes a few more to guarantee the efficient execution of the evacuation programme, I see that as a price worth paying.'

  'You can't push human society that hard. It snaps.'

  'There's no such thing as society,' Minla told him.

  Presently she had the pilot bring them below supersonic speed, and then down to a hovering standstill above what Merlin took to be an abandoned building, perched near the shore amidst the remains of what must once have been a great ocean seaport. The flying wing lowered itself on ducted jets, blowing dust and debris in all directions until its landing gear kissed scorched earth and the engines quietened.

  'We'll take a stroll outside,' Minla said. 'There's something I want you to see. Something that will convince you of our seriousness.'

  'I'm not sure I need convincing.'

  'I want you to see it nonetheless. Take this cloak.' She handed him a surprisingly heavy garment.

  'Lead impregnated?'

  'Just a precaution. Radiation levels are actually very low in this sector.'

  They disembarked via an escalator that had folded down from the flying wing's belly, accompanied by a detachment of guards. The armed men moved ahead, sweeping the ground with things that looked like metal brooms before ushering Minla and Merlin forwards. They followed a winding path through scorched rubble and junk, taking care not to trip over the obstacles and broken ground. Calliope had set during their descent and a biting wind was now howling into land from the sea, setting his teeth on edge. From somewhere in the distance a siren rose and fell on a mournful cycle. Despite Minla's assurance concerning the radioactivity, Merlin swore he could already feel his skin tingling. Overhead, stars poked through the thinning layer of moonlit clouds.

  When at last he looked up, he saw that the solitary building was in fact an enormous stone monument. It towered a hundred metres above the flying wing, stepped like a ziggurat and cut and engraved with awesome precision. Letters in Lecythus A marched in stentorian ranks across the highest vertical face. Beyond the monument, grey-black water lapped at the shattered remains of a promenade. The monument was presumably designed to weather storms, but it would only take one spring tide to submerge its lower flanks completely. Merlin wondered why Minla's people hadn't set it on higher ground.

  'It's impressive.'

  'There are a hundred monuments like this on Lecythus,' Minla told him, drawing her cloak tighter around herself. 'We faced them with whetstone, would you believe it. It turns out to be very good for making monuments, especially when you don't want the letters to be worn away in a handful of centuries.'

  'You built a hundred of these?' Merlin asked.

  'That's just the start. There'll be a thousand by the time we're finished. When we are gone, when all other traces of our culture have been erased from time, we hope that at least one of these monuments will remain. Shall I read you the inscription?'

  Merlin had still learned nothing of the native writing, and he'd neglected to wear the lenses that would have allowed Tyrant to overlay a translation.

  'You'd better.'

  'It says that once a great human society lived on Lecythus, in peace and harmony. Then came a message from the stars, a warning that our world was to be destroyed by the fire of the sun itself, or something even worse. So we made preparations to abandon the world that had been our home for so long, and to commence a journey into the outer darkness of interstellar space, looking for a new home in the stars. One day, thousands or tens of thousands after our departure, you, the people who read this message, may find us. For now you are welcome to make of this world what you will. But know that this planet was ours, and it remains ours, and that one day we shall make it our home again.'

  'I like the bit about "peace and harmony".'

  'History is what we write, not what we remember. Why should we tarnish the memory of our planet by enshrining our less noble deeds?'

  'Spoken like a true leader, Minla.'

  At that moment one of the guards raised his rifle and projected a line of tracer fire into the middle distance. Something hissed and scurried into the cover of debris.

  'We should be leaving,' Minla said. 'Regressives come out at night, and some of them are armed.'

  'Regressives?'

  'Dissident political elements. Suicide cultists who'd rather die on Lecythus than cooperate in the evacuation effort. They're our problem, Merlin, not yours.'

  He'd heard stories about the regressives, but had dismissed them as rumour until now. They were the survivors of the war, people who hadn't submitted eagerly to the iron rule of Minla's new Planetary Government. Details that didn't fit into the plan, and which therefore had to be brushed aside or suppressed or given a subhuman name. He pulled the cloak tighter, anxious not to spend a minute longer on the surface than nec
essary. But even as Minla turned and began walking back to the waiting aircraft - moonlight picked out the elegant sweep of its single great wing - something tugged at him, holding him to the spot.

  'Minla,' he called, a crack in his voice.

  She stopped and turned around. 'What is it, Merlin?'

  'I've got something for you.' He reached under the cloak and fished out the gift she had given him as a girl, holding it before him. He'd had it with him for days, waiting for the moment he hoped would never come.

  Impatiently, Minla retraced her steps. 'I said we should be leaving. What do you want to give me?'

  He handed her the sliver of whetstone. 'A little girl gave me this. I don't think I know that little girl any more.'

  Minla looked at the stone with a curl of disgust on her face. 'That was forty years ago.'

  'Not to me. To me it was less than a year. I've seen a lot of changes since you gave me that gift.'

  'We all have to grow up sometime, Merlin.' For a moment he thought she was going to hand him back the gift, or at least slip it into one of her own pockets. Instead, Minla let it drop to the ground. Merlin reached to pick it up, but it was too late. The stone fell into a dark crack between two shattered paving slabs, Merlin hearing the chink as it bounced off something and fell even deeper.

  'It's gone.'

  'It was just a silly stone,' Minla said. 'That's all. Now let's be on our way.'

  Merlin looked back at the lapping waters as he followed Minla to the moonlit flying wing. Something about the whetstone, something about the tides of that sea, something about the moon itself kept nagging at the back of his mind. There was a connection, trivial or otherwise, that he was missing.

  He was sure it would come to him sooner or later.

  Minla walked with a stick, clicking its hard metal shaft against the echoing flooring of the station's observation deck. Illness or injury had disfigured her since their last meeting; she wore her greying hair in a lopsided parting, hanging down almost to the collar on her right side. Merlin could not say for certain what had happened to Minla, since she was careful to turn her face away from him whenever they spoke. But in the days since his revival he had already heard talk of assassination attempts, some of which had apparently come close to succeeding. Minla seemed more stooped and frail than he remembered, as if she had worked every hour of those twenty years.

  She interrupted a light-beam with her hand, opening the viewing shields. 'Behold the Space Dormitories,' she said, declaiming as if she had an audience of thousands rather than a single man standing only a few metres away. 'Rejoice, Merlin. You played a part in this.'

  Through the window, wheeling with the gentle rotation of the orbital station, the nearest Dormitory loomed larger than Lecythus in the sky. The wrinkled grey sphere would soon reach operational pressure, its skin becoming taut. The final sun-mirrors were being assembled in place, manipulated by mighty articulated robots. Cargo rockets were coming and going by the minute, while the first wave of evacuees had already taken up residence in the polar holding pens.

  Twenty Dormitories were ready now; the remaining eighty would come online within two years. Every day, hundreds of atomic rockets lifted from the surface of Lecythus, carrying evacuees - packed into their holds at the maximum possible human storage density, like a kind of three-dimensional jigsaw of flesh and blood - or cargo, in the form of air, water and prefabricated parts for the other habitats. Each rocket launch deposited more radioactivity into the atmosphere of the doomed world. It was now fatal to breathe that air for more than a few hours, but the slow poisoning of Lecythus was of no concern to the Planetary Government. The remaining surface-bound colonists, those who would occupy the other Dormitories when they were ready, awaited transfer in pressurised bunkers, in conditions that were at least as spartan as anything they would have to endure in space. Merlin had offered the services of Tyrant to assist with the evacuation effort, but as efficient and fast as his ship was, it would have made only a token difference to the speed of the exercise.

  That was not to say that there were not difficulties, or that the programme was exactly on schedule. Merlin was gladdened by the progress he saw in some areas, disheartened in others. Before he slept, the locals had grilled him for help with their prototype atomic rockets, seemingly in the expectation that Merlin would provide magic remedies for the failures that had dogged them so far. But Merlin could only help in a limited fashion. He knew the basic principles of building an atomic rocket, but little of the detailed knowledge needed to circumvent a particular problem. Minla's experts were frustrated, and then dismayed. He tried explaining to them that though an atomic rocket might be primitive compared to the engines in Tyrant, that didn't mean it was simple, or that its construction didn't involve many subtle principles. 'I know how a sailing ship works,' he said, trying to explain himself. 'But that doesn't mean I could build one myself, or show a master boat-builder how to improve his craft.'

  They wanted to know why he couldn't just give them the technology in Tyrant itself.

  'My ship is capable of self-repair,' he'd said, 'but it isn't capable of making copies of itself. That's a deep principle, embodied in the logical architecture at a very profound level.'

  'Then run off a blueprint of your engines. Let us copy what we need from the plans,' they said.

  'That won't work. The components in Tyrant are manufactured to exacting tolerances, using materials your chemistry can't even explain, let alone reproduce.'

  'Then show us how to improve our manufacturing capability, until we can make what we need.'

  'We don't have time for that. Tyrant was manufactured by a culture that had had over ten thousand years of experience in spacefaring, not to mention knowledge of industrial processes and inventions dating back at least as far again. You can't cross that kind of gap in fifty years, no matter how much you might want to.'

  'Then what are we supposed to do?'

  'Keep trying,' Merlin said. 'Keep making mistakes, and learning from them. That's all any culture ever does.'

  That was exactly what they had done, across twenty painful years. The rockets worked now, after a fashion, but they'd arrived late and there was already a huge backlog of people and parts to be shifted into space. The Dormitories should have been finished and occupied by now, with work already under way on the fleet of Exodus Arks. But the Arks had met obstacles as well. The lunar colonisation and materials-extraction programme had run into unanticipated difficulties, requiring that the Arks be assembled from components made on Lecythus. The atomic rocket production lines were already running at maximum capacity without the burden of carrying even more tonnage into space.

  'This is good,' Merlin told Minla. 'But you still need to step things up.'

  'We're aware of that,' she answered testily. 'Unfortunately, some of your information proved less than accurate.'

  Merlin blinked at her. 'It did?'

  'Our scientists made a prototype for the fusion drive, according to your plans. Given the limited testing they've been able to do, they say it works very well. It wouldn't be a technical problem to build all the engines we need for the Exodus Arks. So I'm told, at least.'

  'Then what's the issue?'

  Her hand gripped the walking stick like a talon. 'Fuel, Merlin. You told us we'd find helium three in the topsoil of our moon. Well, we didn't. Not enough to suit our needs, anyway.'

  'Then you mustn't have been looking properly.'

  'I assure you we looked, Merlin. You were mistaken. In fact almost everything you told us to expect on the moon turned out to be wrong. You really didn't pay much attention to it on your way in to Lecythus, did you?'

  'It was a moon. I had a few other things on my mind.'

  'Not only can't we mine it for helium three, but it isn't much good for anything else. The surface gravity's much less than you led us to expect, which complicates our operations tremendously. Things float away at the least provocation. Our experts say the density's so low we shouldn't exp
ect to find anything useful under the crust. Certainly not the heavy ores and precious metals you promised us.'

  'I don't know what to say.'

  'That you were wrong?'

  'I've seen a few moons, Minla. You get used to them. If this one's a lot less dense than I thought, then there's something weird about its chemistry. ' Merlin paused, feeling himself on the edge of something important, but whatever it was remained just out of reach.

  'Well, it doesn't matter now. We'll just have to find fuel from an alternative source, and redesign our fusion drive accordingly. We'll need your help, if we aren't to fall hopelessly behind schedule.' Minla extended a withered hand towards the wheeling view. 'To have come so far, to have reached this point, and then failed . . . that would be worse than having never tried at all, don't you think?'

  Chastened, Merlin scratched at his chin. 'I'll do what I can. Let me talk to the fusion engineers.'