Percy has been living it large in camp halfblood since he and his friends saved Thalia's tree. New demigods have been arriving more often, new monsters have been coming after them, and new quests had been delivered, but all of the peace and tranquility ended when the Oracle prophesized that one of 3 original spawns would usher the doom of the son of the sea. In order to stop this from coming true Percy wound up abandoning camp half blood however he didn't know this was playing into the prophecy. I have not read Percy Jackson books yet I've only seen the two movies.