Heroes of Olympus, The, Book Two: The Son of Neptune

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Jason is a boy who suffers from amnesia. He wakes up on a bus not remembering anything from his past, even who he is, and he was sitting next to Piper, a girl claiming to be his girlfriend, and Leo Valdez, a boy who claims to be his best friend. In a field trip to the Grand Canyon, storm spirits attack the three while their supervising teacher, Coach Gleeson Hedge, reveals himself to be a satyr, and fights for their lives. Jason surprises himself by using a sword disguised as a coin to fight off the spirits, and Coach Hedge is captured while defending them. At the height of the battle, two pegasi land next to them carrying strangers: a girl named Annabeth, a daughter of Athena and a boy with a tattoo of a rainbow named Butch, a son of Iris. Annabeth is angry because she had a vision that she would find a clue to her missing boyfriend, Percy Jackson, at the Grand Canyon. She was told to look for the "one with the missing shoe." Jason, who has lost a shoe in the battle, has no memories of his own identity, let alone Percy Jackson's whereabouts. Jason, Piper and Leo are informed that they are demigods (children of a god and a mortal) and are taken back to Camp Half-Blood where they meet other demigod children like themselves. There, Leo is revealed as a son of Hephaestus, Piper as a daughter of Aphrodite, and Jason as a son of Zeus and the brother of Thalia. He remembers his sister while seeing a picture of her in Cabin One. After scarcely a day after learning about their previously hidden identities, the three receive an urgent quest to rescue Hera, queen of the gods, who was captured by unnamed forces The three friends set off on the back of a giant robotic dragon, Festus (which in Latin means "happy") on a cross-country quest to save Hera and Piper's father from the clutches of Enceladus. Their enemies are under orders from Gaea to reawaken her and overthrow the Olympian gods by pulling up their original roots in Greece. On their way, Jason, Piper and Leo meet Boreas the North Wind (who lives in Quebec city), a trio of cyclopes, the evil enchantress Medea, King Midas, a pack of werewolves and King Lycaon (who got turned into a wolf by Zeus in Mythology) and Lord of the Winds, Aeolus who had given them something very helpful: A picture of a ship with a dragon head that Leo had drawn when he was a small child.. In the end the heroes and their friends, the Hunters of Artemis, manage to save both Piper's father and Hera, whose godly energies were being used to raise the giant Porphyrion. They temporarily stall Gaea's plans, but they will have to face the giants again. With part of his memory returned, Jason realizes that he is a hero from a Roman counterpart to Camp Half-Blood that is somewhere near San Francisco, and that Hera has switched him with the Greek hero Percy Jackson, who is now at the Roman camp with no memory of his life at Camp Half-Blood.