Rachel leads Percy, Annabeth, and Ethan away from Luke’s arena through the Labyrinth with unnerving certainty, avoiding traps and losing their pursuers. In a large columned chamber, Percy realizes Mrs. O’Leary has disappeared, while Ethan rejects Percy’s offer to return to Camp Half-Blood and leaves alone, bitterly insisting that mercy has no place in the war.

The group rests, but tensions rise. Annabeth worries that something was wrong with Luke and resents Rachel’s role as guide, while Rachel tells Percy she can clearly see the path to Daedalus’s workshop and feels guilty that it led through the arena. Percy tries to comfort Rachel, but questions about her family make Rachel withdraw, and Annabeth returns still upset.

In a dream, Percy hears Kronos say Percy has helped ensure Kronos’s rise, then shows Percy Tyson and Grover being attacked by a giant serpent. Percy wakes to an earthquake, and he, Annabeth, and Rachel flee as the chamber collapses. Rachel guides them into a modern steel hallway and to Daedalus’s workshop, marked by a Greek delta.

Inside the workshop, they find advanced inventions, sketches, Greek fire, mechanical wings, and a daylight view of Colorado Springs. Quintus appears and reveals that he is Daedalus, living in his fifth automaton body. Daedalus explains that the Labyrinth is tied to his life but has grown beyond his control, that he has hidden for millennia from death and from Minos, and that he came to camp to judge whether it was worth saving.

Daedalus admits he has already given Ariadne’s string to Luke because Kronos promised him freedom, control of the Underworld, reunion with Icarus, justice for Perdix, and escape from Minos. Annabeth, devastated that her hero has chosen self-interest over wisdom, condemns him. Mrs. O’Leary arrives safely, but Kelli, two Laistrygonians, Minos’s ghost, and a chained Nico burst in; Minos and Kelli reveal that Luke has what he needs and has betrayed Daedalus by handing him over to Minos.

A battle erupts. Rachel seizes the wings while Percy and Annabeth fight Kelli, Mrs. O’Leary and Daedalus battle the giants, and Greek fire spreads. Nico breaks free and, declaring himself the true ghost king, banishes Minos and his summoned spirits into a fissure. Annabeth kills Kelli after Kelli nearly kills Percy, but more monsters approach, so Rachel fits the wings onto herself, Nico, Annabeth, and Percy. Daedalus refuses to abandon Mrs. O’Leary, and the four demigods and Rachel leap from the workshop window into the open sky.