Blackjack carries Percy over Long Island Sound and drops him into the icy water, where Percy uses his powers as Poseidon's son to dive easily in the dark. At the bottom, Percy finds three panicked hippocampi circling a sunken fishing boat and a trapped creature tangled in an abandoned net while the wreck threatens to collapse on it.

Percy discovers the trapped animal is a strange baby cow-serpent, which Percy begins calling Bessie. When Bessie panics at the sight of Riptide, Percy calms the creature and directs the hippocampi to help move the wreckage. Percy then patiently untangles the net by hand, freeing Bessie and earning the gratitude of the sea creatures.

On the flight back, Percy sees Nico hiding near the dining pavilion before dawn. Percy uses Annabeth's invisibility cap to spy alongside Nico and overhears Zoë and Bianca arguing. Zoë reveals that Phoebe cannot join the quest because the Stoll brothers pranked Phoebe with centaur blood, leaving Phoebe bedridden with painful hives.

Bianca worries the prophecy requires five questers, but Zoë resists choosing a replacement. Zoë hints that the camp itself might count as the land without rain and that adding someone else could lead to a worse fate. Bianca urges Zoë to tell Thalia more about Zoë's dream and suspicions about the General, but Zoë refuses and insists they must leave immediately.

After Zoë and Bianca leave, Percy stops Nico from trying to follow the quest. Nico realizes Percy plans to go anyway and begs Percy to watch over Bianca. Percy admits that Percy must help find Annabeth, then makes the dangerous promise to do his best to keep Bianca safe.

Percy runs after the departing quest with only Annabeth's cap, Riptide, and his clothes. As the camp van disappears down the road, Percy worries he cannot keep up, but Blackjack arrives and offers to be Percy’s getaway horse. Percy gratefully accepts and flies after the quest.