Percy Jackson's seventh-grade year has been surprisingly quiet. Not a single monster has set foot on his New York prep-school campus. But when an innocent game of dodgeball among Percy and his classmates turns into a death match against an ugly gang of cannibal giants, things get . . . well, ugly. And the unexpected arrival of Percy's friend Annabeth brings more bad news: the magical borders that protect Camp Half-Blood have been poisoned by a mysterious enemy, and unless a cure is found, the only safe haven for demigods will be destroyed.