After Percy, Grover, and Anabeth come out of the Underworld, they fall into the sea. The Coast Guard finds them and takes them to the Santa Monica Pier. Percy finds out that "the god who has turned" was not Hades. Somebody has stole Zeus' master bolt and stole Hades' helmet. They had pulled out the thief. They had also framed Percy because he is the son of Poseidon and he would have gotten blamed on both sides.
When Percy thinks about this a little more, Ares shows up with a baseball bat placed on his shoulder. He has his motorcycle on him. Percy figures out that Ares tricked him. Ares told Percy that he should have die in the Underworld. All this time Percy had the thunderbolt in his backpack, which was concealed. It was supposed to appear when they went to the Underworld.
Ares tells Percy that he has to kill him. He says that he is good at running away. Percy gets mad and he fights with him.