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 such as being attacked by a minotaur, 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, his best friend Grover is a satyr 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, who they believe is the real thief.

More Info: en.wikipedia.org