"If you build around a river," said Moon slowly, "you reclaim the land to either side. Right? But when you abandon the town, the water table is going to rise because you're no longer pumping out groundwater for industrial use, and you'll get flooded out."

Nobody commented. They walked on, skirting the river and its marshy fringe.

At last they came to the town itself. There was a layout of streets here, you could see that, a roughly rectangular grid laid out over shallow slopes. But the roads were as ruined as the one they had followed here. The buildings themselves were just patterns of mounds and hummocks draped with green, most of them no more than waist height. The whole place looked like an overgrown graveyard. Snowy thought they could have passed by any of these heaps of green-clad rubble in the forest and thought it just another extrusion of rock, the product of nature's mindless churning. Even the vegetation was much the same as in the open land beyond the town. It was only the patterns that told you that hands had built this place, that minds had planned it.

Here and there, though, more enduring fragments poked out of the drowning green. There was one looming, circular hill, as green clad as the rest. Snowy wondered if this might be a keep, the base of one of the Normans' great castles, erected to enforce their occupation of England in the eleventh century. If so, it had lasted where much else had failed. They came across a row of columns, worn to stubs, that looked as if they had been clad in marble. They might have been the grandiose frontage of a bank or town hall.

And here was a statue, fallen on its back. Its face, pocked by lichen and eroded beyond recognition, peered up at the sky from an ocean of green. But the statue bore traces of charring, Snowy saw. He searched for a date, but couldn't find one.

When he dug into the greenery that blanketed other anonymous mounds, he found more traces of fire, of soot and scorching. This place had burned, then, before it had been broken up. He was walking on tragedy, on overgrown horror. He wondered how deep he would have to dig before he found bones.

They came to a comparatively open space. This must have been a central square, maybe a marketplace. Ahmed called a halt. They dropped their packs, drank their water, and peered around. In the lengthening shadows of evening the ruined town was an eerie place, Snowy thought, neither quite natural nor human, neither one thing nor the other.

A little ratty creature scuttled from under Snowy's feet, crisply pattering over the broken asphalt surface and disappearing into the richer green away from the square. It looked like a vole. And, following its tracks, Snowy made out the upright, wary form of a hare. With bewildering speed it turned and scuttled away.

"Voles and hares," he muttered to Sidewise. "I thought we'd see cats and dogs."

Sidewise shrugged, sweat and grime coating his face. "People have gone, right? Civilization has fallen, blah, blah, blah. Cats and dogs were pampered, domesticated, all the genetic variation bred out of them. They wouldn't have lasted long without us."

"I'd have thought cats would survive. Even little kittens used to go hunting."

"Wild cats were perfect killing machines. But the domestic variety had smaller teeth, jaws, brains than their wild ancestors, because old ladies liked them better that way." Sidewise winked. "I always thought cats were faking it. They weren't so tough. Just a pain in the arse."

"Where are the cars?" Moon asked. "I mean, I see the buildings, what's left of them. What about the cars?"

"If you dig in the greenery you might find a few patches of rust, or bits of plastic." Sidewise glared at Ahmed. "What, are you going to chew me out for lowering morale again? I'm only pointing out the bleeding obvious."

"But we don't have to deal with that right now," Ahmed said, with an evenness Snowy admired. "What we need to do do is obvious too." is obvious too."

Snowy nodded. "We have to find shelter."

Bonner clambered up onto a low mound that might once have been a wall. Now he pointed, roughly west. "That way. I can see walls. I mean, standing walls. Something that isn't all covered in shit."

With an unreasonable spark of hope, Snowy got to his feet. It was a church, he saw. A medieval church. He could make out the tall, narrow windows, the high doorway. But the doors and roof had long gone, leaving the building open to the sky. He felt disappointment- and yet a stab of admiration.

Sidewise seemed to share his thought. "If you're going to build, build out of stone."

"Where do you think we are? England, France?"

Sidewise shrugged. "What do I know about churches?"

Ahmed picked up his pack. "All right. There's no roof, so we'll have to make lean-tos. Bonner, Snowy, come with me and we'll fetch some branches. And we'll need a fire. Moon, Sidewise, you attend to that." He looked around at their faces, which were shining like coins in the gathering dark. This would be the first time they had been out of each other's sight since they had woken up, and even Snowy felt a pang of uncertainty. "Don't go too far," Ahmed said gently. "We're alone here. There doesn't seem to be anybody to help us. But we'll be fine so long as we're careful. If anything goes wrong- anything- shout or use your pistol, and the rest of us will come running. All right?"

They nodded and murmured. Then they moved off into the gathering dark, purposefully pursuing their allotted tasks.

The interior of the church was just another patch of greenery. There was a mound at one end that might once have been an altar, but there was no sign of pews or crucifixes, prayer books or candles. The roof was gaping open to the sky, not a trace left of the wooden construction that must once have spanned these slender, sturdy walls.

Under their lean-tos, on pallets of brush, with leaves for blankets, it wasn't going to be such an uncomfortable night. They had all had plenty of survival training; this wasn't so bad compared to that.

They stuck to their survival packs, munching on dried bananas and beef jerky. They didn't eat any of the fruit from the forest. It was a little superstitious, Snowy thought, as if they wanted to cling to what was left of the past as long as possible, before committing themselves to this peculiar new present. But it was OK to take it slow. Ahmed was showing a good grasp of psychology in allowing that. It certainly wouldn't make any difference in the long run.

They were all pretty exhausted after a walk of many klicks on their first day out of the Pit. Snowy wondered how they would have got on if they'd really had to fight; maybe this strategy wouldn't have worked as well as the planners had imagined. And they all had trouble with their feet, with blisters and aches. It was the lack of socks that was the problem. Snowy worried about using up their limited supplies of ointments too fast. They would have to do something about that tomorrow.

But it was comforting to shelter in this relic of human construction, as if they were still cradled by the civilization they had come from. Still, they would keep their fire burning all night.

Snowy was relieved to find he was too tired to think too hard. Still, he woke.

He rolled on his back, restless. The air was hot- too damn hot for an English spring; maybe the climate had changed, global warming gone crazy or somesuch. The sky framed by the open roof was littered with stars, obscured here and there by cloud. There was a crescent moon, too narrow to banish the stars, as far as he could see unchanged from the patient face that had watched over his boyhood. He had learned a little astronomy, during training exercises in the desert, for navigation purposes. He picked out constellations. There was Cassiopeia- but the familiar W shape was extended by a sixth star. A hot young star, maybe, born since he had gone into the Pit. What a strange thought.

"I can't see Mars," Sidewise whispered, from out of the dark.

That startled Snowy; he hadn't known Sidewise was awake. "What?"

Sidewise pointed to the sky, his arm a silhouette. "Venus. Jupiter. Saturn, I think. Where's Mars?"

"Maybe it set already."

"Maybe. Or maybe something happened to it."

"This is bad shit, isn't it, Side?"

Sidewise didn't reply.

"Once I saw some Roman ruins," Snowy whispered. "Hadrian's Wall. It was like this. All grown over, even the mortar rotted away."

"This was a different scale," Sidewise murmured. "Even from Rome. We had a global civilization, a crowded world. Everything was linked up."

"What do you think happened?"

"I don't know. That fucking volcano, maybe. Famine. Disease. Refugees everywhere. War in the end, I guess. I'm glad I didn't live through it."

"Shut up, you two," Ahmed murmured.

Snowy sat up. He peered out through a glassless window frame in the wall of the church. He could see nothing. The land was just a blanket of dark, no glimmer of lights, no glow of streetlights on the horizon. Maybe everywhere was dark like this. Maybe their fire was the only only light in England- on the whole damn planet. It was a stupendous, unbelievable, unacceptable thought. Maybe Sidewise could grasp it properly, but Snowy sure couldn't. light in England- on the whole damn planet. It was a stupendous, unbelievable, unacceptable thought. Maybe Sidewise could grasp it properly, but Snowy sure couldn't.

Some kind of animal howled, out in the night.

He threw a little more wood on the fire, and buried himself deeper in his mound of greenery.

Sidewise had been right. Mars was missing.

The replicators, Ian Maughan's robot probes, had survived. The program had been designed as a precursor to human colonization of the planet. The replicating robots would have been instructed to build homes for human astronauts, to make them cars and computers, to assemble air and water, even grow food for them.

But the humans never came. Even their commands ceased to be received.

That wasn't troubling, for the replicating robots. Why should it be? Until they were told otherwise, their only purpose was to replicate. Nothing else mattered, not even the strange silence from the blue world in the sky.

And replicate they did.

Many modifications were tried, incorporated, abandoned. It did not take long for a radically better design to converge.

The replicators began to incorporate the factory components within their bodies. The new kind looked like tractors, pilotless, trundling over the impassive red dust. Each weighed about a ton. It took each one a year to make a copy of itself- a much shorter reproduction time than before, because they could go where the resources were.

After a year, one of the new replicator types would become two. Which after another year had made two more copies, a total of four. And in another year there were eight. And so on.

The growth was exponential. The outcome was predictable.

Within a century the factory-robots were everywhere on Mars, from pole to equator, from the peak of Mons Olympus to the depths of the Hellas crater. Some of them came into conflict over resources: There were slow, logical, mechanical wars. Others began to dig, to exploit the deeper materials of Mars. If you mined, there was still plenty of resources to go around- for a while, anyhow.

The mines got deeper and deeper. In places the crust collapsed. But still they kept digging. Mars was a cold, hard world, rocky for much of its interior. That helped the mining. But as they dug deeper and encountered new conditions, the replicators had to learn quickly, adapt. They were capable of that, of course.

Still, the penetration of the mantle presented certain technical challenges. The dismantling of the core was tricky too.

Mars weighed one hundred billion billion times as much as any one of the tractor-replicators. But that number was small in the face of the doubling-every-generation rule. Because of the continuing conflicts, the pace of growth was a little slower than optimal. Even so, in just a few hundred generations, Mars had gone, Mars had gone, all but a trace of its substance converted to the glistening bulks of replicators. all but a trace of its substance converted to the glistening bulks of replicators.

With the whole planet transformed to copies of themselves- using solar sails, fusion drives, even crude antimatter engines- the swarm of replicators had moved out through the solar system, seeking raw material.

The next day, roaming into the country around the town, Snowy saw birds, squirrels, mice, rabbits, rats. Once he thought he saw a goat; it fled at his approach.

Not much else. There didn't even seem to be many birds around. The place was silent, as if all the living things had been collected up and removed.

Some of the rats were huge, though. And then there were the rat-wolves he thought he had glimpsed. Whatever they were, they fled at his approach.

Rodents had always been in competition with primates, Sidewise said. Even at the peak of their technical civilization, people had had to be content with keeping rodents out of sight, and out of the food. Now, with people out of the picture, the rats were evidently flourishing.

It was easy to hunt, though. Snowy set a few snares, in a spirit of experimentation. The snares worked. The hares and voles seemed peculiarly tame. Another bad sign if you thought about it, because it meant they hadn't seen humans for a while.

At the end of the second day, Ahmed had them sit in the ruins of the church, in a rough circle on corroded stone blocks.

Snowy was aware of subtle changes in the group. Moon was looking down, avoiding everybody's eyes. Bonner, Ahmed, and Sidewise were watching each other, and Snowy, with calculation.

Ahmed held up an empty ration packet. "We can't stay here. We have to plan."

Bonner shook his head. "The most important thing is finding other people."

"We're going to have to face it," Sidewise said. "There are are no other people- nobody who can help us, anyhow. We haven't seen anybody. We've seen no sign that anybody has been in this area recently." no other people- nobody who can help us, anyhow. We haven't seen anybody. We've seen no sign that anybody has been in this area recently."

"No contrails," Ahmed said, pointing to the sky. "Nothing on the radio, on any frequency. No satellites. Something went wrong-"

Moon laughed hollowly. "You can say that again."

"We can't know how events unfolded. Before the end it must have become- chaotic. We were never recalled. Eventually, I suppose, we were forgotten. Until we were revived by chance."

Snowy forced himself to ask the question. "How long, Side?"

Sidewise rubbed his nose. "Hard to say. If we had an astronomy almanac I guess we could figure it out from the changed positions of the stars. Failing that, your best guess is based on the maturity of the oak forest."

Bonner snapped, "You're so full of shit, you scrawny bastard. How fucking long long? Fifty years, sixty-"

"Not less than a thousand years," Sidewise said, his voice tight. "Maybe more. Probably more, actually."

In silence, they let that sink in. And Snowy closed his eyes, imagining he was plunging off the deck of an aircraft carrier into the dark.

A thousand years. And yet it meant no more than the fifty-year gulf that he thought had separated him from his wife. Less, maybe, because it was just unimaginable. And yet it meant no more than the fifty-year gulf that he thought had separated him from his wife. Less, maybe, because it was just unimaginable.

"Some future this is," Bonner said edgily. "No jet cars. No starships, no cities on the Moon. Just shit."

Ahmed said, "We have to assume we are not going to find anybody else. That we're alone. We have to plan on that basis."

Sidewise snorted. "Civilization has collapsed, everybody is dead, and we're stuck a thousand years in the future. How are we supposed to plan plan for that?" for that?"

"That river is probably clean," Snowy said. "All the factories must have shut down centuries ago."

Ahmed nodded gratefully at him. "Good. At last, something we can actually build on. We can fish, we can hunt; we can start that tomorrow. Sidewise, why don't you use that brain of yours for something useful and think about the fishing? Figure out how we can improvise lines, nets, whatever the hell. Snowy, you do the same for the hunting. Further down the line, we're going to have to find somewhere to live. Maybe we can find a farm. Start thinking about clearing the ground, planting wheat." He glanced at the sky. "What do you think the season is? Early summer? We're too late for a harvest this year. But next spring-"

Sidewise snapped, "Where do you think you're going to find wheat? Do you know what happens if you leave corn or wheat unharvested? The ears fall to the ground and rot. Cultivated wheat needed us us to survive. And if you leave cows unmilked for a few days, they just die of udder bursts." to survive. And if you leave cows unmilked for a few days, they just die of udder bursts."

"Take it easy," Snowy said.

"All I'm telling you is that if you want to farm, you'll have to start from scratch. The whole damn thing, agriculture and husbandry, all over again from wild stock, plants and animals."

Ahmed nodded stiffly. "We, Side. Not you. you. We. We all share the problems here. All right. So that's what we'll do. And in the meantime we gather, we hunt. We live off the land. It's been done before." We. We all share the problems here. All right. So that's what we'll do. And in the meantime we gather, we hunt. We live off the land. It's been done before."

Moon fingered her clothing. "This stuff won't last forever. We'll have to find out how to make cloth. And our weapons will be pretty useless once the ammo is gone."

Bonner said, "Maybe we can make more ammo."

Sidewise just laughed. "Think about stone axes, pal."

Bonner growled, "I don't know how to make a fucking stone ax."

"Neither do I, come to think of it," Sidewise said thoughtfully. "And you know what? I bet there aren't even any books to tell us how. All that wisdom, painfully acquired since we were buck naked Homo erectus Homo erectus running around in Africa. All gone." running around in Africa. All gone."

"Then we'll just have to start that again too," Ahmed said firmly.

Bonner eyed him. "Why?"

Ahmed looked up at the sky. "We owe it to our children."

Sidewise said simply, "Four Adams and one Eve."

There was a long, intense silence. Moon was like a statue, her eyes hard. Snowy noticed how close her hand was to her PPK.

Ahmed got to his feet. "Don't think about the future. Think about filling your belly." He clapped his hands. "Let's move it."