The Sea of Monsters follows the journey of Percy Jackson, a demigod and the son of Poseidon, as he embarks on a quest to save his summer camp, Camp Half-Blood. The camp is threatened by the return of the ancient monster, the Cyclops Polyphemus, who has stolen the Golden Fleece, a magical artifact needed to protect the camp's borders. Percy's adventure begins when he discovers that his friend Grover is in danger and needs rescuing.
Throughout the story, Percy is joined by his friends Annabeth Chase and Tyson, his half-brother who turns out to be a Cyclops. Together, they face various challenges and mythical creatures while navigating the treacherous Sea of Monsters, known in the mortal world as the Bermuda Triangle. Along the way, they learn about loyalty, friendship, and the importance of family, all while trying to complete their mission to retrieve the Golden Fleece.
The narrative ultimately highlights themes of courage and bravery, with Percy confronting not only external monsters but also his internal fears and insecurities. As the trio battles against formidable foes, they grow stronger and more confident in their abilities, reaffirming their bond and commitment to each other. In the end, they succeed in restoring the Golden Fleece to Camp Half-Blood, allowing the camp to continue thriving and serving as a safe haven for demigods.