Percy, Grover, and Annabeth have just escaped the Furies, and now they are traveling across America through the woods. Their walking is interrupted when they come across the Garden Gnome Emporium, which has many startling lifelike status. It also smells deliciously of hamburgers. The hungry heroes enter the emporium and meet Auntie Em, who offers to take care of them even though they have no money. As they settle down to eat, Grover warns that something smells like monsters, but Annabeth and Percy are too hungry to care. Before they leave, they learn that Auntie Em is really Medusa, and by Percy’s swordsmanship and Annabeth’s quick planning they manage to slay the monster. Percy mails Medusa’s head to the Olympians.

As they continue to make their way through the woods, Grover laments over the environmental degradation everywhere around them. He explains that Pan, the great god of the woods, disappeared two thousand years ago and that humans have desecrated the wild ever since. It turns out that Grover risks his life protecting heroes so he can become a Seeker. To seek Pan is not an idle quest, particularly as every satyr who has taken on the search has disappeared.

That night Percy has a dream. In retrospect, Percy thinks that the dream is a message from Hades, asking him to help him rise. However, the next morning, Annabeth suggests that their facts are not adding up. She recalls that the Furies did not seem very aggressive during their attack on the bus. In fact, they were looking for an “it” rather than a “him.” Things may not be what they seem on their quest.

Certainly the emotions of Annabeth and Percy are not what they seem. Percy claims not to care what Poseidon thinks, but Grover suggests that the reason Percy sent Medusa’s head to the gods was to make his father proud of him. Annabeth has a similarly difficult relationship with her father, who viewed her birth as a distraction from his work. Later, after he married another woman, Annabeth’s father and step-mother were cold to her because she attracted monsters. Annabeth ran away when she was seven, and she was only able to reach Camp Half-Blood because her mother guided her to join a group of heroes led by Grover. But one of those heroes died defending the others. Still, although Annabeth pretends not to care about her father, Percy notes that she wears a token in his memory on her necklace.

Grover helps the heroes leave the woods. He finds a pink poodle and befriends it. The poodle has run away from home but knows that there is a two-hundred-dollar reward offered for its safe return. With this money, Percy and his friends are able to buy tickets on Amtrack, and they continue to make their way toward Los Angeles. When they reach St. Louis, Annabeth insists on visiting the Gateway Arch because she hopes to some day design a new monument to the gods that will rival the Parthenon.

However, when they reach the top of the arch, Percy is attacked by Echidna and the Chimera. The monsters were disguised as a woman and a Chihuahua. Echidna reveals that Zeus has authorized her attack on Percy. Although Percy fights bravely, he is bitten by the Chimera’s snake tail. Percy’s sword is knocked away and his clothes are on fire, so he jumps off the arch, hoping that he will land in water below and that Poseidon will save him.