Scott Westerfeld presents the sequel to his hit steampunk novel, Leviathan. In the midst of conflict with the Clankers, the Darwinists' war efforts rely on the behemoth, the largest, most feared creature in the British navy. Deryn, posing as a boy so that she may serve in the Air Service, finds herself aboard the Leviathan along with Alek, the heir to the empire, who is also in disguise. However, when the Leviathan's mission goes awry, Alek and Deryn...

Alek and Deryn encounter obstacles on the last leg of their round-the-world quest to end World War I, reclaim Alek's throne as prince of Austria, and finally fall in love.