In the distant future, when cities move about and consume smaller towns, a fifteen-year-old apprentice is pushed out of London by the man he most admires and must seek answers in the perilous Out-Country, aided by one girl and the memory of another.

In a post-apocalyptic world where cities ride on wheels and consume each other to survive, two people meet in London and try to stop a conspiracy.

"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, the Jenny Haniver, 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...