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 that can end the war. But whose side he really on? While on their top-secret mission, Alek finally discovers Deryn’s deeply kept secret. Two, actually. Not only is Deryn a girl disguised as a guy… she has feelings for Alek.