Percy Jackson, the demigod son of Poseidon, is accused of stealing Zeus's lightning bolt. Percy embarks on an adventure with his friends Annabeth Chase and Grover Underwood to uncover the truth and rescue his mother from the Underworld.

After Camp Half-Blood's protective border is breached, Percy Jackson embarks on an epic odyssey into the Sea of Monsters in search of his best friend, the satyr Grover Underwood, and the one thing that may save the camp — the legendary Golden Fleece. Aided by demigods Annabeth Chase and Clarisse La Rue, along with his cyclops half-brother Tyson, Percy's survival becomes the key to preventing Luke and the Titan Kronos from bringing down Camp Half-Blood — and, ultimately, Olympus.

The stakes are higher than ever before as Percy is faced with the sudden disappearance of Annabeth and the impending Great Prophecy provided by the Oracle of Delphi, dictating the fate of Olympus. As foretold by the Oracle of Delphi, one demigod child of the "Big Three" is fated to raise Olympus to new heights or bring it crashing into ruin, with their own life hanging in the balance.