Kin said she didn't believe it.

'You couldn't take a Neolithic farmer and turn him into a planetary engineer,' she protested.

WE COULD. THE DISC BUILDERS CONSTRUCTED US CLEVERLY.

'You won't even tell me about the builders!' The screen went blank.

Whump. Kin gripped the edges of the couch. Whump. The roc didn't fly, it simply bullied its way through the upper air, shovelling it aside with a sneer.

Talking was difficult when g-forces slapped and banged with a horrible rhythm. Silver managed it with the least discomfort.

'I don't believe it either,' she said. 'I can see what a device like the Disc would need.' Whump. 'Need a sapient caretaker. No machines could handle all the problems that might crop.' Whump. 'Might crop up. But unless the creature was already a technical sophisticate, he would simply become mad.'

Kin braced herself for the next wingbeat. It didn't come. Beyond the window she could see the roc's wing outstretched, the tips of the huge feathers vibrating in the slipstream. The bird was starting its glide.

Half the Disc was spread before the canted cabin. Kin rolled out of her couch and swayed across the trembling deck until she could grasp a bulkhead.

The world was a bowl of jewels flung across the sky. Ahead, wearing the setting sun like the gemstone on a ring, was the Rim Ocean.

Roc slid on down the sky, staring at the sun with terrible bird eyes. Sometimes she shrugged her shoulders to dislodge the ice, which flashed and tumbled as it began the long fall.

Kin knelt on the floating platform and watched the microfigures of Silver and Marco thread their way through the tunnels.

Elsewhere Disc machines were lurching into action. She wondered what would have happened if some medieval farmer was Chairman now. Could he have helped the Computers start the long repair?

She stood up and ordered the platform to the walkway at the rim of the map hall, and hurried up the worn stairs to the interface room.

HALLO, said the screen.

'You don't need me,' said Kin. 'I've given you all the instructions you need to repair yourself. It will take you a long time, but you can do it without affecting the biosp -- oh boy, the biohemisphere, I suppose -- too much. But you can't go on like it -- not unless you get fresh materials from outside.'

WE KNOW. ENTROPY IS AGAINST US.

'You can't go on cannibalizing old machines for spare parts. You may last another hundred years, that's all.'

WE KNOW.

'Do you care about the people on the surface?'

THEY ARE OUR CHILDREN.

Kin stared at the glowing letters. Then she said softly: 'Tell me about Jago Jalo. He must have seemed a godsend.'

YES. WE WERE ALREADY AWARE THAT THE DISC WAS DOOMED. IN THOSE DAYS WE MAINTAINED AN ARRESTOR SCREEN AGAINST METEORITES. IT WAS COMPARATIVELY EASY TO EXTRACT THE RESIDUAL VELOCITY FROM HIS SHIP. WE WATCHED HIM BRING HIS SMALLER SHIP WITHIN THE VAULT OF HEAVEN. UNFORTUNATELY WE COULD NOT CONTACT HIM. THAT SHOULD HAVE MADE US SUSPICIOUS.

'You allowed him to land, though.'

UNFORTUNATELY HIS SHIP ATTRACTED THE ATTENTION OF A ROC DURING THE DESCENT.

'A roc?'

A LARGE BIRD.

'I don't believe it' said Marco. 'I see it, but I don't believe it. It's going to take us home, is that it?'

Below them land flashed past in a dusty blur. There was a brief impression of surf and then the roc was arrowing out to sea.

'Didn't you see the big egg in that garden where you were caged?' said Kin weakly. 'Didn't you wonder what laid it? Of course it can't take us home, it's just a big bird. I saw the specifications, back in the Hub.'

'It seems a little stupid to say this in the circumstances,' said Silver, 'but such a creature could not exist in flesh and blood. It would collapse under its own weight.'

'It doesn't weigh more than five tonnes,' said Kin. 'It's one of the Disc builders' finest constructions. It's alive. It's got sinews like Line cord and its bones are pneumatic. Just tubes filled with gas under pressure. The Computers showed me. Marvellous, isn't it?'

'Why is it losing height? We'll land in the sea,' said Marco.

'Yes,' said Kin. 'I should get back into your couch if I were you.'

'You mean we are going to land in the sea?'

Marco looked down at the rushing waves. They were low enough for every crest to be visible. Then he looked at what, on the Disc, had to be called the horizon. The sun was just a red glow, half hidden by strips of cloud, tipping the wave tops with fire. Marco thought.

'Oh no,' he said. Tell me I'm wrong. Tell me you're not planning to do what I think you are planning to do...'

'If it helps you any,' said Kin. 'Jago Jalo was insane even by the standards of an insane age.'

IT BECAME OBVIOUS. WE HAD NOT CONSIDERED THAT ANY RACE WOULD SEND ITS MADMEN INTO SPACE.

'In a ship like this, only a madman would go.'

HE CAME TO THE HUB WITH A DEMOUNTED GEOLOGICAL LASER. HE KILLED THE CHAIRMAN OF THE TIME.

'You didn't try to stop him?'

WE WERE NOT INSTRUCTED TO DO SO. BESIDES, THE MAN WAS OBVIOUSLY FROM A TECHNOLOGICAL CULTURE. WE HAD TO WEIGH THE FUTURE OF THE DISC. HE ORDERED US TO BUILD HIM A SHIP. IT WAS NOT DIFFICULT. WE CALCULATED THAT IF WE ASSISTED JAGO JALO BACK TO HIS HOME WORLD IT WOULD NOT BE LONG BEFORE WE HAD FURTHER VISITORS. THEREFORE WE SENT WITH HIM ONE OF OUR SPY BIRDS -- THE RAVENS, THE EYES OF GOD, OUR BEAUTIFULLY CREATED BIRDS.

"Then why didn't you contact us as soon as we arrived? Hell, I've had fleas, I've nearly been burned alive, I was shoved in a seraglio--'

WE DECIDED TO OBSERVE YOU FIRST. WE COULD NOT BE SURE THAT JALO WAS AN EXCEPTION AND THEN THE FOUR-ARMED CREATURE ADDED WEIGHT TO OUR SUSPICIONS.

Kin watched the letters fade. She said: 'You know that we can build worlds. Proper worlds. Planets. We could build a planet for the Disc people. You know it is a fair copy of my home world?'

YES.

'Do you know why?'

YES.

'Will you tell me?'

The screen stayed blank for several seconds. Then it was filled with words, so many that the Computers had had to reduce the size of the letters. Kin stood up and read:

YOU WISH TO KNOW ABOUT THE DISC BUILDERS. YOU WISH TO KNOW THE REASONS BEHIND THE CONSTRUCTION OF THE DISC. WE CAN TELL YOU. BUT IT IS OUR ONLY BARGAINING COUNTER ON BEHALF OF OUR CHILDREN. IT IS POSSIBLE THAT YOU COULD LEAVE AND RETURN TO PLUNDER THE DISC, AS JALO HAD INTENDED. WE COULD NOT STOP YOU. YET WE REALIZE THAT KNOWLEDGE IS A PRIZE YOU GREATLY DESIRE. WE WILL GIVE YOU KNOWLEDGE. YOU WILL BUILD A NEW WORLD FOR OUR PEOPLE.

Kin had already been considering it. It would mean building a G-type star within a few light-minutes of the Disc, unless there was a suitable one that could be moved...

'We'd need access to Disc technology,' she said. Teleportation, the force-grow vat theories, the lot.'

YOU WOULD HAVE IT, OF COURSE.

'Then you will have your new world. If the Company won't do it, I could float a Company of my own with that bait. I could go to one of the small operators -- yes, I'll do it.'

WE HAVE A BARGAIN.

'Just like that? You don't need any -- well, I guess I can't give you any sureties,' said Kin, surprised.

WE HAVE OBSERVED YOU. WE ESTIMATE THERE IS A 99.87 PER CENT CHANCE THAT YOU WILL HONOUR THE BARGAIN. DON THE HELMET.

Kin looked up at the padded metal rim above her head.

WE TRUST YOU. TRUST US. THE HELMET WILL LINK YOU TO CERTAIN CIRCUITS DESIGNED FOR THIS SITUATION. WE CAN GIVE YOU NOT INFORMATION BUT KNOWLEDGE, THAT YOU WILL OBTAIN NOWHERE ELSE IN THE UNIVERSE.

'The purpose of life is to find things out,' said Kin doubtfully.

YES. WHO WOULD SHUN KNOWLEDGE?

Kin sighed, reached up, grasped, pulled.

The robots were busy in the centre of the deck. One of them rolled towards the horseshoe panel, trailing a cable behind it. The rest were clustered around an oddly bent piece of mirror-bright rod. When Kin looked at it her eyes ached. It seemed to be twisted in ways that normal matter just couldn't go, which meant she was looking at the heart of a matrix drive.