Danny Caulfield's quiet Christmas break from Wilsons, the school for spies, is shattered by gunshots and a heartrending discovery about his parents. That same night, he's summoned to Wilsons' to prepare for a mission: under an assumed identity, Danny must find a way to protect the Treaty Stone that keeps peace between the Upper and Lower worlds. Meanwhile, the evil Ring of Five pursues Danny, for he is the true Fifth --only Danny can unite the members of the Ring and awaken their full powers as master spies.