Percy and Annabeth reach Polyphemus’s island and are surprised to find it beautiful and fertile rather than desolate. They sense the Golden Fleece in the great tree above the ravine, but they quickly discover why taking it will not be simple: the giant sheep in the meadow are carnivorous and strip a deer to bones in seconds. They also spot the other lifeboat from the CSS Birmingham, which convinces them to delay any attempt on the Fleece and search first for Grover, Clarisse, and possibly Tyson.

They hide the Queen Anne’s Revenge, climb the cliffs, and overhear voices below them at the Cyclops’s cave. Looking down, Percy and Annabeth see Polyphemus, Grover in a wedding dress, and Clarisse hanging upside down above a boiling pot. Clarisse accidentally exposes Grover by calling him a satyr, forcing Polyphemus to realize his bride is not a Cyclops. Grover stalls for time by claiming he will taste better cooked with mango chutney, but Polyphemus decides to postpone the wedding until sundown and locks both Grover and Clarisse inside the cave.

Percy and Annabeth cannot move the boulder sealing the cave, and Percy realizes brute force will not save their friends. Watching Polyphemus manage his separate flocks, Annabeth decides they must rely on trickery. Her plan is for Percy to hide beneath one of the sheep and enter the cave with the flock at sunset while she remains outside to create a distraction.

The plan works at first: Percy rides into the cave under a sheep, and Annabeth enrages Polyphemus by calling herself "Nobody," reviving the old insult from Odysseus’s trick. Furious, Polyphemus chases Annabeth and forgets to reseal the cave. Percy finds Grover trying unsuccessfully to free Clarisse, cuts Clarisse loose with Riptide, and learns that Tyson was not in Clarisse’s lifeboat. Before they can escape or help Annabeth, an explosion sounds outside and Percy hears Annabeth scream, ending the chapter with the rescue still in danger.