The son of neptune

The Son of Neptune by Rick Riordan is the second book in the Heroes of Olympus series. It follows Percy Jackson, who has lost his memory and is living at a camp for Roman demigods called Camp Jupiter. Percy soon learns that he is the son of Neptune (the Roman counterpart of Poseidon) and must join forces with two other demigods, Hazel Levesque and Frank Zhang, on a dangerous quest to free the Greek god of death, Thanatos, from the clutches of the giant Alcyoneus. Their mission is crucial to preventing the rise of the ancient giants and stopping the awakening of the earth goddess, Gaia