Clarisse, the daughter of Ares and longtime enemy of Percy, is given the quest to go into the Sea of Monsters to bring back the Golden Fleece, which has healing powers for plants, animals, and humans. Percy and Annabeth decide to go also, not just for the Golden Fleece, but for their friend Grover who is trapped in Polyphemus' cave. Tyson, a young Cyclops whom Percy befriended at school that year, joins them on their journey. Tyson is Poseidon's son and therefore Percy's half-brother.