With the great Traction City of London completely destroyed, Tom Natsworthy and Hester Shaw travel across the world, trading with other airships and adventuring on the exciting and exotic routes of the Bird Roads. When their little scrapyard aircraft is pursued by rocket-firing gunships, the ice city of Anchorage offers them sanctuary. But as Tom and Hester soon discover, it is no safe refuge. Devastated by plague in recent years and haunted by ghosts...

In a world of drones and androids Zen Starling is a human thief, but mostly he just likes to ride the Interstellar Express, the sentient trains that travel through the K gates from planet to planet, something only the Guardians understand--but now the mysterious Raven wants him to steal the Pyxis, an object that could either open up a new gate, challenging the Guardians, or put the entire gate system, and the universe itself in danger.

Zen Starling, a small-time thief, and Nova, an android girl come from the Network Empire, whose stations are scattered across the galaxy and linked by the K-gates and the sentient trains travel at light speed between them--but the gate through which they just passed was a new one, and they have no way of knowing into what danger it might have led them.