Now it's up to Percy and his friends: Their arch-enemy Kronos is preparing to strike and is marching toward Olympus, right into the heart of New York. Meanwhile, the Olympian gods have all left to fight against the resurrected monster Typhon. Together with Artemis's Hunters and the awakened monuments of the city, the young demigods are trying to defend the seat of the gods, but unfortunately, they also have a spy in their midst. At least one goddess has remained in Olympus.