Infants of Olympus: The Hands of Glycon

(taking place after the Heroes of Olympus) Percy Jackson and Annabeth Chase have lived peacefully in Camp Jupiter since the fall of Gaea. But when they come to visit Camp Half-blood at the start of the summer, they heroes and their friends are pushed head-first into a crazy quest with a villain that is unlike any they've faced before...for he holds not the fate of the world in his hands, but the sanity of the demigod heroes.