In the fourth and final brilliant installment of Philip Reeve's
award-winning quartet, after twenty years, the devastating world
war between the predatory Traction Cities and their enemies is
ending. Wren and her father Tom Natsworthy travel the Bird
Roads in their airship, trying to forget Hester's betrayal. But
in the ruined wreckage of the city of London they make a discovery
that changes everything. And Hester faces an implacable foe with
the means and the will to destroy the entire human race.
