She was glad -- she'd had a horrible thought about what would happen if one didn't get built.

The robots had also built a proper pilot's seat in front of the controls. Marco was sitting in it, swearing.

'It'll be like finding a hole in fog,' he said. 'I hope your tin friend builds good jets.'

'The hole will show up on the screen,' suggested Silver.

'Yeah. But we'll be going at a hell of a lick. Kin, are you sure it's all worked out?'

Kin smiled. 'Right down to the Disc's tumbling speed and the rotation of the Vault of Heaven. Don't you believe that machines capable of running the Disc for seventy thousand years are capable of--'

'--threading a needle ten thousand miles away by dropping the thread over a waterfall? No. I want a chance to experiment with the jets.'

'You'll have it.'

The roc's wingbeats thundered in the night as it wheeled about and skimmed across the dark water. It dropped the ship, fought frantically for height again, wingtips brushing the waves.

There was a moment of free-fall, then a slap as the ship hit. It bobbed, and spun slowly.

The roc passed across the stars, wings booming, heading back to its secret valleys. And Kin relaxed. Through the hull of the ship there came a new sound, a soft murmur as of distant engines. The Rimfall.

She waited, with the soft padding of the helmet pressing against her closed eyes. Nothing happened.

Then she remembered. It came as a shock, but that dwindled as She took control over the body. How could She have forgotten? Then She remembered about that, too. Unless One forgot, how could One learn?

She could feel Kin somewhere in Her mind, a little flask of tastes and textures, senses and experiences. Around Her She could experience the Disc, and She knew there was danger there. It would be too easy to lose Herself in the sheer exhilarating enjoyment of it. She turned her mind back to the Computers.

You have done well.

THAT WAS MY TASK.

I will allow some recollection to Kin Arad. She is Me, after all. She will awake knowing something about Us. And she will understand about the Disc.

YES.

She reached into the mind within Her and made certain amendments. Then, contented, She let Herself forget...

Kin remembered. The memories were there, cold, hard, real, like shards of ice in the mind. She recalled the Disc.

'The Disc,' she said, her voice flat in the shock of it, 'is the boot in the coal measure, the coin in the crystal. The filling in the tooth of the triceratops. The secret mark that reveals the maker. They couldn't resist it. They built a perfect universe to specifications, but they couldn't resist adding the Disc out here, hard to find, but a clue. How do I know?' she shouted.

The screen stayed blank.

'I know it. They weren't just the Disc builders. They built the lot -- the real Earth, kung, all the stars. They laid down our fossils. We thought maybe the Great Spindle Kings had done that, but the Spindle Kings never existed. They were all part of the false strata of the new universe. We wondered if we'd evolved with the help of the Kings. We never evolved! We were created, just like we recreate whales and elephants for our colony worlds.

'We're a colony universe. The Builders just moved in and built it, and because everyone needs a history, they gave us a history. Just as we do with the new worlds. Ancient bones. Fabulous monsters. Great Spindle Kings, Wheelers. And we never realized it. We did it ourselves, and we never tumbled to it.

'Then one of them built the Disc. Almost as a joke, maybe? Certainly for no important reason. An exercise in ingenuity. It must have been an afterthought, a collection of neat ideas, put together after the main work was done.

'Seventy thousand years! That's the age of the universe -- it's hardly got its paint scratched! We thought it was four billion years old. The evidence said that it was, and we believed in the evidence.'

She leaned back. She could still feel the memories there, like old facts forgotten until now. She probed them gingerly, as a tongue explores a hollow tooth.

'Old. Intelligent. Divorced from matter. That's how I remember the Builders. Each one bigger than we can imagine, or maybe smaller, because -- because there would be nothing to measure, except the ego. I said old? Even their age couldn't be measured, because until they built the universe there was no time. Am I right?'

WE CANNOT ANSWER THAT QUESTION BRIEFLY. WE KNOW NOTHING OF THEM OTHER THAN THAT WHICH THEY TOLD US.

'What do you know of them, then?'

BEFORE THEM, THERE WAS ONLY PROBABILITY. THEY IMPOSED A PATTERN ON THAT PROBABILITY.

'Why?'

YOUR COMPANY BUILDS WORLDS. THERE IS NO REAL NEED. YOUR NATAL WORLD IS NOT OVERPOPULATED. WHY?

'Once we were overpopulated. And we found that the more people there were, the more they were the same. It was the only way we could survive. People had always dreamed of a unified world. We thought it would be a richer one. It wasn't. It meant that the Eskimo got educated and learned cost accountancy, but it didn't mean that the German learned to hunt whales with a spear. It meant everyone learned how to press buttons, and no-one remembered how to dive for pearls.

'Then the Mindquakes got us. That would have been -- yes, a couple of years after the Terminus probes. People just died. Died in their billions, too, their minds just kind of folded in on themselves.

'Afterwards, we had to start over. At least we had all the toys of the Spindle Kings to play with, and we could spread out -- we had to spread out, after the Quakes. They made us look hard for mental elbow-room, new worlds where we could flee and learn the forgotten ways. We had built robots to remember some of them for us!

'We thought it was natural, a trodden path. You see, we had the example of the Spindle Kings. We thought that any intelligent species filled its home world until the sheer mind pressure started killing them off, and then the survivors embarked on interstellar colonization; whatever way they rationalized it, the real reason would be a fierce desire to escape from other people. And then, since usable worlds aren't that common, they'd start to learn planetary engineering. Oh, we had it all carefully calculated. Race after race, fruiting and bursting across the evolving galaxy, creating new worlds before they died and in the process making new seed-beds for new races. I wrote a book about it, called Continuous Creation, haha.'

NOW YOU CAN WRITE THE SECOND EDITION.

'It'll be a bit short, I'm damn sure about that. What can I say? "The lights in the sky are scenery"?'

WHY NOT?

'You haven't told me why the -- Builders built.'

The words flashed on to the screen immediately, as if the Computers had been preparing them.

HUMANS ARE INQUISITIVE. THAT IS A FUNCTION OF THEIR HUMANITY. THE BEINGS THAT BUILT THIS UNIVERSE DID SO BECAUSE IT WAS UNTHINKABLE THAT THEY SHOULD NOT. CREATION IS NOT A THING THAT GODS DO, IT IS SOMETHING THAT THEY ARE.

'And afterwards? What did they do next?'

There was white water around the ship. Kin could see a little tree-shrouded island beyond one port, a humped black shape in the twilight, and could feel the hull bouncing over the water. The sky wheeled. There was no jolt, it was simply that now the floor was just a wall. Foam covered the ports for a moment, and then Kin could look -- down.

The Rimfall hung before them, looking exactly like a luminous white road. Marco in the pilot's seat was outlined against it, and Kin could see that he had instinctively braced himself with his feet scrabbling for a hold.

Down, way down, there was a ball of fire in the sky. The Disc was in darkness now, but the little orbiting sun was giving a brief day to the face of the waterfall. While Kin watched, it climbed above her and disappeared as the ship overtook it.