After dark at Geryon’s ranch, Nico performs a summoning ritual beside a pit, intending to call Bianca di Angelo. The ghost of King Minos drinks from the offering first and tries to turn Nico against Percy, Annabeth, Grover, and Tyson. Minos reveals that he has been protecting Nico, claims the Labyrinth belongs to him, admits he caused madness in intruders such as Chris Rodriguez, and warns that Daedalus cannot be trusted.

Bianca finally appears and calms the other spirits. Percy apologizes for her death, but Bianca says she chose her own fate and does not regret it. Bianca tells Nico that he cannot bring her back, that his true anger is toward her for leaving him and dying, and that holding grudges is dangerous for a child of Hades. Bianca also confirms that she sent Percy the Iris-messages so Percy could find Nico. When the dead grow agitated, Bianca warns that Nico’s power is drawing Kronos’s attention and returns to the Underworld.

That night Percy dreams of Luke in a completed fortress on Mount Tam, where warriors are preparing for an assault. Kelli leads Kampê to Luke, and Kampê demands revenge after the heroes freed Briares. Luke reluctantly accepts Kampê into the force and gives her Ariadne’s string, while Kelli hints at Luke’s uneasy role in destroying Camp Half-Blood and then deliberately tears Percy out of the dream.

Percy’s dream shifts to Daedalus on a tower with his young nephew Perdix. Perdix proves himself a brilliant inventor and suggests combining mechanics and magic to preserve a soul in an artificial body. Daedalus, jealous and threatened, lures Perdix toward the edge and lets the boy fall. Athena condemns Daedalus for killing a boy under her blessing, and Percy wakes shaken by the vision of the inventor they are seeking. Grover, awake nearby, realizes seven days have passed since the group left camp because time moves strangely in the Labyrinth, meaning his deadline to find Pan has expired.

In the morning, Nico refuses Percy’s offer to come along, saying he needs time to think, while Eurytion promises to keep him safe and changes the ranch’s future away from sacred cattle meat. Eurytion gives Annabeth a one-use silver disc from Hephaestus that becomes a mechanical spider and leads the group back into the Labyrinth toward Hephaestus’s forges. Following the spider, the group reaches a chamber guarded by a Sphinx, who turns her old riddle challenge into a standardized test. Annabeth refuses to answer because the questions reward random facts rather than thought, so the Sphinx attacks. Tyson, Percy, Grover, and invisible Annabeth escape after Tyson destroys the grading machine and Grover animates broken pencils into plants that delay the monster.