Percy Jackson is a normal boy until he discovers he is a demigod, half human and half god. His math teacher turns into a monster and tries to kill him. Percy's best friend Grover senses danger and they flee, pursued by the monster. Percy's mother is killed by the monster. Percy collapses at a farmhouse and learns at Camp Half-Blood that he is the son of Poseidon. On his first quest to retrieve Zeus' stolen lightning bolt, Percy faces many dangers but ultimately discovers Luke stole the bolt and returns it to Zeus.