After escaping Kampê, Percy, Annabeth, Grover, Tyson, and Briares stop in a waterfall-filled chamber above a pit that Briares says leads to Tartarus. Briares reveals that his two Hundred-Handed brothers have faded because they lost the will to remain immortal. Tyson begs Briares to help defend Camp Half-Blood, and Percy tells Briares about Luke, Daedalus, and Kronos, but Briares says he cannot help and leaves, devastating Tyson.

The group camps in an older marble corridor that Annabeth hopes is near Daedalus’s workshop. Tyson mourns Briares and loses faith in his former hero, while Percy tries to reassure him. During watch, Annabeth admits the quest is not going logically and that she does not know where the Labyrinth is taking them. Percy asks about Hera’s hints and the last line of Annabeth’s prophecy, but Annabeth refuses to discuss it in the dark. Percy also realizes Nico may have entered the Labyrinth and may now be pursuing him.

When Percy sleeps, he dreams of Daedalus and Icarus preparing bronze wings in Daedalus’s prison workshop. King Minos breaks in too early, but Daedalus and Icarus escape through a heat vent and fly away from Crete. Icarus becomes reckless in his freedom, the wings begin to fall apart, and Icarus plummets into the sea while Daedalus cries out for his son.

After the group continues through the maze, stone passages shift into earth tunnels. They find a grave-like pit smelling of the Underworld, with a cheeseburger wrapper and remains that show Nico has been summoning the dead. Percy, feeling Nico is close, runs ahead and emerges through a cattle grid into a ranch full of red cattle sacred to Apollo. Eurytion, a son of Ares and the ranch’s cowherd, finds them with his two-headed dog Orthus and warns them to return to the maze before taking them to his boss.

At the Triple G Ranch, the group meets the three-bodied Geryon and finds Nico di Angelo staying there. Nico angrily accuses Percy of letting Bianca die, while Geryon reveals that Nico is being advised by the ghost of King Minos and that Luke will pay well for powerful half-bloods, especially Nico. Geryon seizes Nico and plans to sell him to the Titan army, but Percy bargains for everyone’s freedom by agreeing to clean the filthy, flesh-eating horse stables by sunset. If Percy fails, Geryon will sell Percy’s friends and Nico to Luke.