Percy, Annabeth, and Nico rush from Manhattan toward Camp Half-Blood after learning Rachel has taken Blackjack. Because city traffic is gridlocked and the pegasi are gone, Percy summons hippocampi from the polluted East River, including Rainbow, to carry them quickly to Long Island Sound.

At camp, Argus confirms Rachel has arrived, but the Big House is surrounded by green light and magical Mist. Chiron, badly injured but lucid, explains that he invited Rachel after she had a vision suggesting Hades’s curse on the Oracle might be lifted. Percy tries to stop Rachel, fearing she will suffer May Castellan’s fate, but an invisible barrier prevents him from reaching her.

The old Oracle’s mummy emerges from the Big House as Apollo appears and formally asks Rachel whether she accepts the risk and destiny of prophecy. Rachel pledges herself to Apollo and the spirit of Delphi; green smoke leaves the mummy, the corpse crumbles to dust, and Rachel collapses. After a tense moment, Rachel survives and Apollo announces her as the new Oracle of Delphi.

Almost immediately, Rachel speaks a new Great Prophecy about seven half-bloods, storm or fire, an oath kept with a final breath, and foes reaching the Doors of Death. Rachel does not remember saying it, and Apollo warns there is no use questioning her. Rachel tells Percy she now understands her gift and her destiny, then gives him a meaningful goodbye before resting in the Big House.

Campers return from New York, the wounded are treated, and funeral rites are held. Silena is honored jointly by the Aphrodite and Ares cabins, with her betrayal left unspoken, while Ethan Nakamura receives a shroud reflecting his devotion to balance and the minor gods. Dinner is subdued, though Grover’s reunion with Juniper brings a moment of joy, and Nico is openly accepted after helping save the camp.

That night Annabeth finds Percy at the Poseidon table with a blue birthday cupcake, reminding him that he turned sixteen the day the prophecy was fulfilled. Percy admits that thoughts of Annabeth helped anchor him to mortality and influenced his refusal of godhood. Annabeth kisses him, but the campers interrupt and dump them in the canoe lake; Percy creates an air bubble underwater, giving the two a private and happy kiss.