Percy visits the camp arena and is immediately tackled by Mrs. O'Leary, the friendly hellhound he inherited. Playing fetch with the dog reminds Percy that Beckendorf had cared for her and made her collar and chewing bone, deepening Percy's grief over Beckendorf's death.

Mrs. O'Leary leads Percy into the woods to the old Council of Cloven Elders' clearing, where Juniper is confronting Leneus about Grover's disappearance. Leneus dismisses Grover as a traitor because Grover reported Pan's death, but Percy defends Grover and points out that the satyr leaders themselves seem scattered and afraid.

When Leneus refuses to help, Percy grabs him and warns that Kronos's war will threaten satyrs and nature spirits too. Percy orders Leneus to act like a leader, find Grover, and bring Juniper news. Leneus runs away angrily, while Juniper remains worried because she cannot leave the forest to search for Grover herself.

After Juniper vanishes to avoid Mrs. O'Leary, Nico tells Percy that Beckendorf's ghost does not blame Percy and has chosen to stay in Elysium while waiting for someone. Nico also confirms that Percy's vision of Nico near Mount Tam was real; Nico had been following a lead about his own family, though he refuses to explain further.

Nico presses Percy to accept the extreme plan he has been proposing as the only way to defeat Luke and Kronos. Percy hesitates, but Nico argues that Typhon is coming, the camp is divided, and the demigods cannot withstand the Titan army without Percy gaining a similar power to Luke's. Remembering Annabeth's accusation and the danger to camp, Percy agrees.

Nico says they must first retrace Luke's past by visiting Luke's mother, May Castellan, in Westport, Connecticut. Instead of using pegasi, Nico teaches Percy that Mrs. O'Leary can shadow travel through darkness. Percy climbs onto Mrs. O'Leary, tells her their destination, and the hellhound charges straight into an oak tree, carrying Percy into freezing shadows.