Percy goes to the Oracle. The oracle tells him that hill will fail to save the thing that matters most.
Chiron asks Percy if he will accept the quest to go to the underworld and get back the lightning bolt before the summer solstice. He needs to go to Los Angeles with grover and Annabeth.
Percy, Annabeth and Grover took a bus out of New York. Mrs.Dodds and two other Furies disguised as old women were also onboard. The bus crashes, and everyone evacuates except for Percy, Grover, Annabeth and the three furies. In the end Percy manages to kill them with his sword "Riptide", which he got from Chiron.
The Bus Trip
Medusa disguised as Aunty Em invites them into her shop, she gives them something to eat and drink. Aunty Em then talks about her past, Annabeth and Grover then figures out who she is and saves Percy from looking in her eyes. Percy then manages to chop off hear head and kill her.
They then took the train, and had to stop for three hours. The three of them visited St. Louis Gateaway Arch. Percy had to wait to take the elevator because all three of them could not fit with all of the people. There was also an old lady there waiting. She then turned into a Chimera. Percy got heavily wounded and was forced to jump down 600ft into the Mississipi River.
Ares comes to them while they eat at a diner and says if they help him retrieving his shield back he will get them a ride to Las Vegas. It's in a love tunnel at a theme park. When they get into the tunnel they get trapped. They somehow manages to escape and returns Ares his shield. Percy is not happy of being used by Ares.