The Son of Neptune is a 2011 fantasy-adventure novel written by American author Rick Riordan, based on Greek and Roman mythology. It is the second book in The Heroes of Olympus series, preceded by The Lost Hero and followed by The Mark of Athena. The story follows the adventures of amnesiac Percy Jackson, a demigod son of Poseidon, as he meets a camp of Roman demigods and goes to Alaska with his new friends Hazel Levesque and Frank Zhang to free the Greek god of death, Thanatos, and help save the world from Gaea, the earth goddess. The novel is narrated in third-person, switching between the points of view of Percy, Frank, and Hazel.