Nine months after Percy Jackson's defense of Mount Olympus in The Last Olympian, Percy finds himself alone and on the run from monsters in northern California without his memories. With the guidance of Lupa, the wolf-goddess and protector of ancient Rome, he makes his way to Camp Jupiter, the Roman demigod training camp and counterpart to the Greek demigods' Camp Half-Blood. Upon arriving, he is attacked by Gorgons — Stheno and Euryale — and successfully defends a disguised Juno and the camp with the help of the guards on duty. Having been protected by Percy during the attack, Juno announces Percy's arrival with approval, identifying him as a son of Neptune. She tells him privately that he can only regain his memory by learning to be a hero again and successfully surviving the challenges he encounters at camp.