Clara said, ‘Actually, you could zigzag up and down the corridor on a trajectory that would last for eons, but we settled on a better solution than that. If you shadow a world in the orthogonal cluster, we can read the future density of dust in the region by inspecting its surface. That’s the helpful thing about a time-reversed planet: it gives you a forecast that can’t be wrong.’

Valeria couldn’t fault the woman’s imagination. At the very least, she must have gone to one of Yalda and Eusebio’s recruiting lectures when they were trying to assemble the crew for the Peerless. Maybe she’d even signed up, but then lost her courage at the last moment.

‘Here we are,’ Clara announced.

Valeria had been expecting some kind of conical structure adorned with parachutes, contrived to resemble one of the test rockets that had made short flights and returned, but perhaps Clara hadn’t been close to the real project after all. The object sitting on the sand, a few saunters from the road, looked like a small stone cabin on stilts, with the upper parts of each wall tilted outwards so that the windows they bore faced down at an angle. Just getting the bizarre construction here must have involved quite an investment – but what advantage did the woman hope to garner?

The four of them trudged across the desert together. Silvio looked even more contemptuous of the whole farce than Valeria, but he said nothing.

‘Where are the engines?’ Valeria asked.

‘Underneath, of course.’ Clara gestured to the bottom of the floor, about a stride above the ground. Valeria ducked down between the stilts.

‘There’s nothing here but a kind of . . . black mirrorstone,’ she reported. It was hard to see much by starlight, but the surface looked utterly smooth and unbroken. ‘Where does the exhaust come out?’

‘There is no exhaust. Just light.’

‘Light? Your rocket runs on light, but no one spotted you descending?’

‘Ultraviolet light,’ Clara persisted. ‘The faster the light a rocket uses, the less heat it generates in the process.’

Valeria emerged and straightened up. ‘Let me guess: your vehicle suffered some damage in the landing, but with sufficient funds you could get it working again. Your backers will be rewarded, of course, with new inventions that will put them so far beyond their rivals—’

Eusebio said angrily, ‘Enough! Whatever you believe, this woman is my guest, and I won’t allow you to talk to her that way.’

Clara said, ‘Scepticism is an admirable trait, and we seem to have confused everyone by arriving early.’ She turned to Valeria. ‘My vehicle suffered no damage. And I promised you a ride.’

Valeria stared at her. ‘You want to . . . ?’ She pointed upwards.

‘Yes. Eusebio? Will you come with us?’

He said, ‘If you’re sure you’re not too tired.’

‘I’m not a pilot; the photonics – the machines – will do everything for us. Silvio?’