Alek and Deryn are aboard the Leviathan when the ship is ordered to pick up an unusual passenger. This brilliant yet maniacal inventor claims to have a weapon called Goliath that can end the war. But whose side is he really on?

While on their top-secret mission, Alek finally discovers Deryn's deeply kept secrets. Two, actually. Not only is Deryn a girl disguised as a guy, but she also has feelings for Alek.

The crown, true love with a commoner, and the destruction of a great city all hang on Alek's next—and final—move.

The thunderous conclusion to Scott Westerfeld's Leviathan series.