Young Percy Jackson discovers he is the son of the Greek god Poseidon.

Percy is accused of stealing the lightning bolt of Zeus and must undertake a dangerous journey to find and return the lightning bolt and prevent a war between the gods. Together with his friends Annabeth and Grover, Percy travels across America, encountering various mythical creatures and facing challenges. They discover that the real thief is the god Ares, who is being manipulated by the greater threat, the Titan Kronos. At the end of the series, Percy and his friends manage to prevent a war between the gods and save Olympus. He returns to the demigod camp, where he continues his adventures and develops his abilities as a demigod.