After returning home from his boarding school for the summer, Percy and his mother Sally Jackson, travel to their cabin in Montauk. However, the trip is cut short and after a series of harrowing incidents, Percy finds himself at Camp Half-Blood, a training camp for demigods like him. He discovers that he is a demigod son of Poseidon, the Greek god of the sea, and that the gods are accusing him of having stolen Zeus' master lightning bolt. To clear his name and save the world from another war between the Olympian gods, he sets out to retrieve the lightning bolt from Hades whom they believe is the real thief. Thus Percy Jackson and his companions, a satyr named Grover Underwood and Annabeth Chase, a daughter of Athena, start on a journey to the underworld, facing numerous mythological monsters on the way. After confronting an innocent Hades, they learn that their friend Luke Castellan, son of Hermes, is the real thief who stole the bolt to allow Kronos, the defeated king of the Titans, a chance to rise again.