Nico uses shadow travel to bring Percy and Mrs. O’Leary to a wooded cliff in Connecticut near Luke Castellan’s childhood home. Mrs. O’Leary is exhausted by the trip and falls asleep, leaving Percy and Nico to visit the house on foot. The strange yard, wind chimes, old toys, mirrors, candles, and decaying food suggest that Luke’s mother has been waiting obsessively for Luke’s return for years.

May Castellan welcomes both boys as if each is Luke and serves endless peanut butter sandwiches, Kool-Aid, and burned cookies. Through her confused conversation, Percy and Nico learn that May could see through the Mist, had once been offered an important but dangerous job, and was left damaged by visions she could not escape. May remembers that Luke ran away in third grade, supposedly to protect her from monsters, and later returned with his scar but still with blue eyes, meaning the visit happened before Kronos possessed him.

Nico presses May for what Luke wanted during that later visit, and May reveals that Luke asked for her blessing before going to a river. This confirms Nico’s theory about the ritual Percy hopes to attempt. May then briefly changes: her eyes glow green, her voice deepens, and she cries out about protecting her child from his fate before collapsing and returning to confusion. Percy and Nico flee, shaken by the glimpse of what May’s sight and Luke’s fate have done to her.

Back at the cliff, Percy and Nico find Hestia, goddess of the hearth, calmly tending a fire beside Mrs. O’Leary. Hestia feeds them and explains that May was born with the gift of sight but went too far, and that understanding Luke requires understanding his family. When Percy blames Hermes for abandoning Luke and May, Hestia cautions Percy against easy judgment and speaks about the difficult power of yielding, explaining that she gave up her Olympian throne to preserve peace.

Hestia identifies herself as the last Olympian and tells Percy to remember her when he faces his final decision. Percy chooses to continue the quest, and because he made a sacrifice to Hestia, the goddess sends Percy, Nico, and Mrs. O’Leary to Percy’s home. Their sudden arrival wrecks Sally and Paul’s apartment, but Paul reacts with wonder and finally accepts the reality of Percy’s demigod life.

At the kitchen table, Percy and Nico explain Typhon, Kronos’s coming invasion, and Nico’s plan. Nico says Percy needs Sally’s blessing because the dangerous process has only succeeded before when a mother willingly accepted the risk for her son. Sally struggles but, encouraged by Paul and understanding Percy’s necessity, gives Percy her blessing. Sally asks Percy to send a blue signal from Olympus if he survives, and Nico then says they do not need to go to Los Angeles because there is a closer entrance to the Underworld.