Once home to the most advanced civilization on Earth, Atlantis is now an underwater kingdom ruled by the power-hungry King Orm. With a vast army at his disposal, Orm plans to conquer the remaining oceanic people and then the surface world. Standing in his way is Arthur Curry, Orm's half-human, half-Atlantean brother and true heir to the throne.

In their quest to confront the ultimate evil, Percy and his friends battle swarms of mythical creatures to find the mythical Golden Fleece and to stop an ancient evil from rising.

Accident prone teenager, Percy discovers he's actually a demi-God, the son of Poseidon, and he is needed when Zeus' lightning is stolen. Percy must master his new found skills in order to prevent a war between the Gods that could devastate the entire world.