The story is set in New York City, where unusual events are unfolding, such as Poseidon, a giant Greek god, emerging from the sea and shrinking to human size. He walks to the Empire State Building to confront his brother, Zeus, about a missing lightning bolt. Zeus suspects that their children might be involved in the theft, but Poseidon defends his son, Percy, insisting that he is just a regular boy unaware of the existence of gods.