The Son of Neptune (Heroes of Olympus 2)

Percy Jackson, son of Poseidon, God of the Sea, has woken from a very deep sleep and come face to face with two snake-haired ladies who refuse to die.
But they’re the least of his problems. Because Percy finds himself at a camp for half-bloods, which doesn’t ring any bells for him. There’s just one name he remembers from his past. Annabeth.
Only one thing is certain – Percy’s questing days aren’t over. He and fellow demigods Frank and Hazel must face the most important quest of all: the Prophecy of Seven.If they fail, it’s not just their camp at risk. Percy’s old life, the gods, and the entire world might be destroyed . . .