Ptaclusp hadn't got where he was today - no, he'd have to correct himself - hadn't got to where he had been last night without eventually seeing the advantages in the Unlikeliest situations.

'He'll save on clothing,' he said slowly. 'I mean, he can just paint it on.'

'I don't think you've quite got the idea, dad,' said IIb wearily. He sat down beside his father and stared across the river to the palace.

'Something going on over there,' said Ptaclusp. 'Do you think they've noticed the pyramid?'

'I shouldn't be surprised. It's moved around ninety degrees, after all.'

Ptaclusp looked over his shoulder, and nodded slowly.

'Funny, that,' he said. 'Bit of structural instability there.'

'Dad, it's a pyramid! We should have flared it! I told you! The forces involved, well, it's just too-'

A shadow fell across them. They looked around. They looked up. They looked up a bit more.

'Oh, my,' said Ptaclusp. 'It's Hat, the Vulture-Headed God...'

Ephebe lay beyond them, a classical poem of white marble lazing around its rock on a bay of brilliant blue-

'What's that?' said Ptraci, after studying it critically for some time.

'It's the sea,' said Teppic. 'I told you, remember. Waves and things.'

'You said it was all green and rough.'

'Sometimes it is.'

'Hmm.' The tone of voice suggested that she disapproved of the sea but, before she could explain why, they heard the sound of voices raised in anger. They were coming from behind a nearby sand dune.

There was a notice on the dune.

It said, in several languages: AXIOM TESTING STATION.

Below it, in slightly smaller writing, it added: CAUTION - UNRESOLVED POSTULATES.

As they read it, or at least as Teppic read it and Ptraci didn't, there was a twang from behind the dune, followed by a click, followed by an arrow zipping overhead. You Bastard glanced up at it briefly and then turned his head and stared fixedly at a very small area of sand.

A second later the arrow thudded into it.

Then he tested the weight on his feet and did a small calculation which revealed that two people had been subtracted from his back. Further summation indicated that they had been added to the dune.

'What did you do that for?' said Ptraci, spitting out sand.

'Someone fired at us!'

'I shouldn't think so. I mean, they didn't know we were here, did they? You needn't have pulled me off like that.'

Teppic conceded this, rather reluctantly, and eased himself cautiously up the sliding surface of the dune. The voices were arguing again

'Give in?'

'We simply haven't got all the parameters right.'

'I know what we haven't got all right.'

'What is that, pray?'