Percy refuses to let Annabeth scout Luke’s suite alone, so Percy, Annabeth, and Tyson gather their supplies and sneak through the cruise ship together. On the way, they hear Chris Rodriguez, a missing camper from Hermes cabin, talking with another ally of Luke’s, which confirms Luke has recruited half-bloods. Looking down into the ship’s central mall, Percy and Annabeth also see a large gathering of monsters watching a young warrior destroy a dummy dressed in a Camp Half-Blood shirt, showing that Luke is building an army for open war.

Near the admiralty suite, Tyson uses his sharp hearing to imitate the voices inside and accidentally alerts Luke and his guards. Luke captures them in his luxurious stateroom, where Percy sees the most disturbing object aboard the ship: a huge golden sarcophagus that radiates cold. Luke introduces the twin bear-men Agrius and Oreius, then calmly admits that he poisoned Thalia’s tree. He argues that the gods ruin mortal lives and insists Thalia would have supported him, while Annabeth angrily rejects him and calls him a monster.

Luke tries to break Percy and Annabeth’s loyalty by revealing that he has spies at camp, knows their plan to seek the Golden Fleece, and knows more about the prophecy tied to Percy’s sixteenth birthday than Percy does. When Percy says Hermes sent them, Luke explodes with hatred toward his father and points to the sarcophagus, explaining that a titan lord is slowly re-forming there as more half-bloods join his cause. Luke offers Percy wealth and Annabeth glory if they join him, but Annabeth refuses. Luke then summons enchanted human security guards and orders Oreius to take Percy, Annabeth, and Tyson below to feed an Aethiopian drakon.

While being marched across the deck, Percy realizes Oreius is weaker without Agrius beside him and signals Tyson to strike. Tyson knocks Oreius away, Annabeth disables one guard, and Percy stops the other only after the alarm is raised. Monsters and crew flood the deck, including armored fighters, hellhounds, and giant archers. With no safe route left, Percy, Annabeth, and Tyson scramble into a lifeboat. Percy fights off attacks with Riptide, then cuts the ropes, sending the lifeboat plunging off the ship toward the ocean.