After the Battle of the Labyrinth, the rest of summer at Camp Half-Blood feels strangely normal. Campers return to training, games, campfires, and pranks, while Percy spends time with Tyson and Mrs O’Leary. Percy and Annabeth remain emotionally distant because any discussion of Kronos leads back to Luke, whom Annabeth still cannot talk about openly.

On the last day of camp, Percy prepares to leave for Manhattan while Annabeth stays behind to help Chiron and study Daedalus’s laptop before returning to San Francisco. Percy presses Annabeth about the final line of her prophecy, and Annabeth reveals it: she would “lose a love to worse than death,” which she connects to Luke’s fate as Kronos’s host.

Hera appears and claims the quest was a success because the Olympian “family” is safe, dismissing the deaths and losses of Luke, Daedalus, Pan, and the danger to Nico. Percy accuses Hera of helping only when it served her idea of a perfect family, and Annabeth agrees, rejecting Hera’s demand for gratitude. Hera threatens Annabeth before vanishing in divine light, deepening the sense that the gods’ help can come with dangerous costs.

Two days later, Percy celebrates his fifteenth birthday at home with Sally, Paul Blofis, and Tyson. Paul privately tells Percy that he is thinking of proposing to Sally and asks how Percy feels; Percy supports the idea because Paul makes Sally happy and has helped Percy. Poseidon then unexpectedly arrives, awkwardly meets Paul, greets Tyson, and takes Percy aside.

In the kitchen, Percy tells Poseidon everything about Kronos, Luke, and the Labyrinth. Poseidon confirms that full war is approaching, explains that Luke may have to be killed to defeat Kronos, and reveals that the sea is already at war among the old sea gods. Poseidon gives Percy a sand dollar as a birthday gift to use at the right time, reassures Percy that Antaeus’s cruelty does not reflect Poseidon’s will, calls Percy his favorite son, and warns that Typhon is stirring beneath Mount St Helens and will eventually head for Olympus in New York.

After the party, Percy reflects on his camp beads, the looming prophecy, Rachel, and Calypso. Remembering Calypso’s request, Percy plants the moonlace sprig she gave him in a planter on the fire escape, where it grows into a glowing silver plant. Nico di Angelo suddenly appears, reports that Daedalus has received a fitting afterlife punishment as a builder in Asphodel, and says he has discovered what may be the only way Percy can beat Luke; Percy invites Nico inside for birthday cake so they can talk.