Percy found a casino to stay the night at and they were given a flow to eat that made them forget everything and stay at the casino. Percy first found out what was happening when a man told him that it was still 1977. They were trapped in the casino for 5 days.
Returning the Lightning Bolt
Entrance to the Underworld
Percy goes into the ocean of Los Angeles and a water spirit gives him three pearls to escape the underworld. They then find a shop called Crusty's Water bed palace. Grover and Annabeth tries some water beds and suddenly they are trapped. Percy tricks the owner to try the water bed himself and then Percy traps him. He frees his friends and behind the desk in the store, they find the entrance to the underworld.
Hades is not happy to see Percy since he thinks Percy stole the lightning bolt and the helm of darkness. Hades tells Percy to hand over both of the items. Percy says he has neither of them. Hades then tells Percy to open his backpack. Percy does, and then he sees the lightning bolt. Percy then realizes that Ares tricked them, since he gave Percy that backpack. Percy, Grover and Annabeth then step on the pearls and got sent back to Santa Monica beach.
Percy accuses Ares for stealing the items, but Ares says he made someone steal it for him. Ares has Hades' helm of darkness at his bike. Ares and Percy start to fight and Percy tries to get in the water since there he will have an advantage. Percy then manages to throw a huge wave at Ares and knocks him over. Percy then stabs Ares in his ankle. Mrs.Dodds the furie watched the whole thing and Percy then gave Mrs.Dodds the helm of darkness back.
Percy took a plane from LA to New York even though he shouldn't since it's Zeus' territory. He then took the elevator in the Empire state building to the 600th floor. There on the thrones sat his father Posideon and his uncle Zeus. He explained everything to them and gave Zeus his lightning bolt back. Posideon also tells Percy that his mother is back alive in their apartment. Percy goes home to see her, but decides to stay at the haflblood camp.
Percy has a good time the rest of the summer, but can't decide whether he will stay at the camp for the whole year or go home. The last day, Percy and Luke will go into the forest to kill some monsters. Luke betrays Percy and sends a scorpion on him before they leave. Percy kills the scorpion, but gets bitten. After that he gets healed and decides that he will go home.