Since the universe could not be said to have a natural ending, because the universe was not natural but only the sum of the lives that had shaped it, Men intended to live for ever. Why not?

Preserve meme pools, preserve ideas, that was the secret. If you had a hundred planets there was room for different sciences, curious beliefs, new techniques, old religions to flourish in quiet corners. Earth had been one united civilization and had nearly perished once because of it. Diversify enough, and somewhere you'll always find someone capable of catching anything the future throws at you.

People on a disc guarded by demons and ringed with a waterfall, what memes would they contribute to the genetics of civilization? She tried to explain to Marco.

'What are memes?' said Marco.

'Memes are -- ideas, attitudes, concepts, techniques,' said Kin. 'Mental genes. Trouble is all the memes likely to develop on the disc are host-destructive. Anthro-pocentricity is one.'

A pale red moon rose above the curdled clouds. Now they flew a mile apart, flew high and fast to make the hours count. Kin kept an eye on the speck that was Silver, and worried.

Quite wrong, of course, to project human thought patterns on an alien, but a man in Silver's position would live in hope that sooner or later food would be forthcoming. Men were optimists.

You couldn't expect a shand to think like a man. It was so easy to think of your friends as humans in a skin, and for good and noble reasons people were encouraged to think of aliens as funny-shaped men. Just because they learned to play poker or read Latin didn't make them human.

In short, Kin wondered when Silver would attempt suicide. She signalled Marco and told him.

'We can do nothing,' he said. 'I have already decided to eat no food until we reach the hub, as a gesture of solidarity. We could take disc proteins, if the 'waiter's analysis was right,' he added.

'Will that make her feel better?'

'It may make us feel better. However, there is another problem that has recently forced itself on my attention. I hesitate to mention it--'

'Mention it, mention it.'

'Look at the panel on your left wrist. There's an orange fluorescent line against a green strip. See it?'

Kin squinted down in the flickering light.

'I see it. Only it's an orange dot.'

'Quite, but it should be a line. We really are running out of gas, Kin.'

They flew in silence for a while. Then Kin asked, 'How long?'

'About six hours for you and me. Perhaps an hour less for Silver. That will solve one problem. She'll come to earth miles behind us.'

'Except that we will of course stay with her,' said Kin flatly. Marco appeared not to have heard.

'If we still had the 'waiter the problem would not have been insurmountable. The hub is not too far. We could have terrorized disc people into transporting us. A hundred suggestions leap to the mind. It might have been quite enjoyable, and good experience.'

'Experience for what?'

'Hobnobbing with the disc folk on a superior basis. I had planned, should the hub hold nothing of interest, to set up an empire. Surely the idea had occurred to you?'

It had, in passing. Kin thought for a while of Genghis Marco, Marco Caesar, Prester Marco. He could do it, at that. A four-armed god king.

'How long would you say it would take the disc to get on to a space-going footing?' he asked. 'If that was made a goal, I mean? We have the knowledge.'

'No, we don't. We think we do, but all we know is how to operate machines. Of course, you could get a spaceship built inside a decade.'

'That soon? Then we could--'

'No we couldn't.' Kin had been thinking about this too. 'What could be built is a primitive capsule powered by solid-fuel rockets with enough oomph to ram the outer dome. You could launch it by dropping it over the waterfall.'

'First we'd have to unify the disc,' said Marco thoughtfully. 'Not difficult. Give me five hundred Norsemen and--'

'There's Silver,' said Kin. 'And anyway, I have great hopes for the hub.'

Even so...

She had been doing a lot of thinking, before they lost the 'waiter. With the 'waiter they might have conquered the disc, filling the void left by the presumably departed disc creators. Without it, the best they could hope for was a comfortable life. In a strange way it wouldn't be so bad for the other two. They would be aliens, marooned on a strange world. She would be marooned among people. It was possible that she had more in common with Silver and Marco than she did with the barbarians down there. It was a dreadful possibility.

"These belts are supposed to be able to fly you halfway across a system and land you on a planet,' she complained.

'They were not expected to carry people thousands of miles against gravity, including many changes of altitude,' said Marco. 'It is most vexing.'

'Vexing!'

'If you feel so strongly, I suggest you make a complaint to the manufacturers.'

'How can -- was that a joke?' said Kin. 'Good grief!'

Dawn saw them flying over semi-desert and scrub, in a sky free of clouds. Once they passed over a camel train, almost invisible were it not for its skeletal juddering shadow on the sand.

They had drifted slightly off their course during the night, and as far as Marco could estimate were speeding down the Tigris-Euphrates valley.

'That puts us in south-east Turkey,' said Marco, and added wistfully, 'That means Baghdad. I should like to have seen Baghdad.'

'Why?' said Kin.

'Oh, when I was a kid my foster-folks bought me a book of fantasy stories about, well, genies and magic lamps and such. It made a big impression on me.'

'Don't suggest landing,' said Kin. 'Don't even think about it.'

But they passed over a city of low white houses surrounding palaces and strangely domed buildings. A tent town lay outside the walls. The river the city straddled was noticeably a different colour downstream, and low enough between its banks to speak of drought.

Now the sun was well up the ground shimmered.

A mile later Silver's belt failed. There was no question of a crash -- instead all forward power ceased as the batteries' waning ergs buoyed her gently to the ground.

The others followed her down into a grove of knotted, sweet-smelling trees. When Kin took off her helmet the heat hit her like the breath of Hell. Too hot, she decided. No wonder the fields looked scorched. From here the river was a blood-coloured snake winding weakly between slabs of cracked mud.

'Well,' she said vaguely. She meant This Is It.

'I am at a loss,' said Marco, moving hurriedly into the heady shade under the trees.

'You mean you don't have a plan?'

'Your meaning?'

'Oh, forget it.' Kin took a sip of water from the suit's reservoir. Have to be careful about that, too.

Silver sat with her back against a trunk, staring vaguely at the city. Behind her the sun was a copper rivet in a sky like hot iron. Then she commented. 'An aircraft has just risen.'

He was old in looks at least, his face wrinkled like an old apple. His grey beard was intricately styled. His eyes seemed to show neither whites nor expression. Certainly he did not seem surprised.

Disc builder? While Kin watched him and Silver talking, facing each other cross-legged under the trees, she thought hard and fast. His clothing didn't look anything but barbarously splendid, but she was no arbiter of disc fashion. His craft was technologically advanced, and he knew how to use it -- at the moment it was folded up inside a pouch on the belt of his travelling companion, a large broad man wearing nothing but a loincloth and a dour expression. He held a long curved sword, and his eyes never left Marco.

Kin slid across to the kung.

'I wonder where he keeps his antipersonnel blaster?' she asked. 'Marco, you know you and Silver had this idea about how I could survive on the disc by using sex?'