Goliath

Alek and Deryn are aboard the Leviathan when the ship is ordered to pick up an unusual passenger. This brilliant, maniacal inventor claims to have a weapon called Goliath. It can end the war. But whose side is the inventor really on? While on their top-secret mission, Alek finally discovers Deryn's deeply kept secret. Not only is Deryn a girl disguised as a boy . . . 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.