Demi-god Percy Jackson and his friends must journey into the Sea of Monsters to save their camp. But first Percy will discover a secret that makes him wonder whether being claimed as Poseidon's son is an honor or a cruel joke.

When Zeus and his fellow Olympians encounter Cerberus, a snarling, three-headed dog, in the Underworld, Hades must conquer his fears and tame the hound so everyone can continue into the Underworld and deposit their Titan prisoner, Oceanus, back where he belongs.

Zeus and his fellow gods-in-training face a new challenge in the underworld when they attempt to capture Cerberus—the three-headed guardian and cherished pet of Zeus’ brother Hades—but find themselves up against more than they bargained for when they have to face off against Melinoe, the Greek goddess of ghosts, nightmares and funerary rites, and her skeletal minions.