It is the cusp of World War 1, and all the European powers are arming up. The Austro-Hungarians and Germans have their Clankers, steam-driven iron machines loaded with guns and ammunition. The British Darwinists employ fabricated animals as their weaponry. The Leviathan is a living airship, the most formidable airbeast in the skies of Europe.

Aleksandar Ferdinand, prince of the Austro-Hungarian Empire, is on the run. His own people have turned against him. All he has is a small, loyal crew of men.

Deryn Sharp is a commoner, a girl disguised as a boy in the British Air Services. She's a brilliant airman. But her secret is in constant danger of being discovered.

With the Great War brewing, Alek and Deryn's paths cross in the most unexpected way...