Percy Jackson, a 12-year-old boy, discovers that he is a demigod, the son of Poseidon. After being attacked by monsters, he is taken to Camp Half-Blood, where he learns that Zeus’s lightning bolt has been stolen and that Poseidon is being blamed.
To prevent a war between the gods, Percy is given a quest to find and return the stolen lightning bolt. He travels across the United States with his friends Annabeth and Grover, facing many mythological dangers along the way.
In the end, Percy discovers the real enemy behind the theft, recovers the lightning bolt, and restores peace between the gods. He also begins to understand his identity and powers, setting the stage for future adventures.