But she could not forget him. How brave he had been on Cloud 9. And that good-bye kiss, on the Kom Ombo air quay, amid all those oily ropes and heaped-up sky train couplings and shouting stevedores and roaring engines. Wren had never kissed anyone before. She hadn’t known quite how you went about it; she wasn’t sure where her nose was meant to go; when their teeth banged together, she was afraid that she was doing it all wrong. Theo had laughed, and said it was a funny business, this kissing, and she said she thought she might get the hang of it with a little more practice, but by then the captain of his airship was hollering, “All aboard that’s coming aboard!” and starting to disengage his docking clamps, and there had been no time…

And that had been six months ago. Theo had written once—a letter that reached Wren in January at a shabby air caravanserai in the Tannhäusers—to tell her that he had made it home safely and been welcomed by his family “like the prodigal son” (whatever that meant). But Wren had never managed to compose a reply.

“Bother!” she said, and ordered another coffee.

Tom Natsworthy, Wren’s father, had faced death many times, and been in all sorts of frightening situations, but he had never felt any fear quite so cold as this.

He was lying, quite naked, on a chilly metal table in the consulting room of a heart specialist on Peripatetiapolis’s second tier. Above him a machine with a long and many-jointed hydraulic neck twisted its metal head from side to side, examining him with a quizzical air. Tom was pretty sure that those green, glowing lenses at its business end were taken from a Stalker.