Agents for peace are bringing an end to the devastating conflict
between the roaming Traction Cities and their fanatical enemies
while Wren and her father Tom travel the Bird Roads in their
airship, trying to forget that Hester has betrayed them. In the
ruined wreckage of the city of London they make a discovery that
will change the world, while Hester must face an implacable foe
with the means and the will to destroy the entire human race. The
fourth, spectacular instalment of the award-winning quartet.