Silvio said, ‘Thanks, but I should watch the truck.’

Clara led Valeria and Eusebio up the short flight of stairs and through the doorway. Valeria’s gut was squirming: she didn’t know what she believed any more, but just letting the woman take charge felt dangerous.

A little starlight entered through the cabin’s thick windows; Valeria could make out four couches and what looked like a tank of compressed air. Clara said, ‘Lights,’ and three large panels in the ceiling immediately began to glow. Valeria reached up and pressed her fingers to the illuminated surfaces; she could feel no heat, and the light was impossibly steady for any kind of lamp.

‘How . . . ?’ she pleaded.

Clara said, ‘Nothing I say would make any sense to you until you’ve learnt about the energy levels in a solid. But don’t worry, I’m sure I could bring you up to speed in about a stint.’ She gestured at the couches. ‘It shouldn’t be bumpy at all, but the protocol is to strap in during take-off.’

Valeria lay down on one of the couches and Clara helped her with the harness before attending to Eusebio.

‘There should be a reception at the university tomorrow, or the Council chambers,’ he babbled.

‘I’ll be happy to talk to anyone, anywhere,’ Clara assured him. ‘Anyone but jailers.’

She climbed onto her own couch. ‘Pilot?’ A diagram appeared on the wall, as self-luminous as the ceiling panels. After a moment, Valeria thought she recognised it as a topographical map of Zeugma’s environs.

Conjurors could do all kinds of things with lenses and hidden lamps. But they were getting close to the moment of truth, and if this woman had secreted a few hefts of sunstone above the smooth black panel in the floor with the hope of actually making this cabin fly, the only effect it was likely to produce would be to incinerate them all.

‘Pilot: plan a vertical ascent to an altitude of five slogs, followed by a return to our starting point, with a maximum deviation of one part in six from standard gravity.’

The topographical map tilted and became something like an artist’s rendering of the landscape. Then the viewpoint ascended to take in an ever wider portion of the desert, while a dashed red line rose up from the ground, sprouting strange annotations.

Valeria said hurriedly, ‘I believe you! We don’t have to do this!’ In truth she still doubted the woman’s story, but she did not want to be proven right and consumed by flames.

Clara buzzed mischievously. ‘Don’t be a killjoy. Pilot: execute the plan.’

Valeria felt a gentle pressure pushing her into the couch, as if someone had placed a young child on her belly. She looked to the window; they really were ascending, albeit with an impossible grace. No one could have done this but a traveller returned.