The Son of Neptune recap

Percy Jackson, his memory erased except for the name Annabeth, is chased by monsters to Camp Jupiter, the hidden camp of Roman demigods. There he befriends Hazel, a daughter of Pluto with a secret past, and Frank, a shy son of Mars. Guided by the goddess Juno, the three are sent north to Alaska to free Thanatos, the god of death, who has been chained by a giant so that slain monsters can no longer die and stay dead. Along the way Hazel confronts the truth that she once lived, died, and was returned to the world, and Frank learns his life is bound to a fragile piece of firewood. They reach Alaska, release Death, and defeat the giant Alcyoneus. Racing back, they save Camp Jupiter from an invading army of monsters and giants. Percy's full memory returns, Frank and Percy are made praetors, and at the very end a Greek warship, the Argo II, descends on the Roman camp carrying Jason, Piper, Leo, and Annabeth, bringing the two camps face to face at last.

Previously: In the Percy Jackson stories, Percy, a son of the sea god, and his friends defeated the Titan lord Kronos and saved the gods, winning a promise that all demigod children would be claimed and honored, and a new Great Prophecy foretold seven half-bloods facing a threat rising from the earth. In the first Heroes of Olympus book, that threat took shape: the primordial earth goddess Gaea began to wake and raise the giants, ancient enemies of the gods. A boy named Jason arrived at Camp Half-Blood with no memory, and the queen of the gods, Hera, revealed she had swapped him with Percy. Jason, it turned out, was a Roman demigod from a separate hidden camp, and the Greek and Roman camps, long kept apart and hostile, would have to unite to survive. Percy, his own memory wiped, was sent to the Roman side. As this book opens, he is a stranger with no past, hunted by monsters and searching for a camp he cannot remember.

The quest succeeds: in the frozen land of Alaska, beyond the reach of the gods, the three heroes break the chains binding Thanatos, the god of death, whom the giant Alcyoneus had imprisoned to keep monsters and the dead from ever staying dead. Hazel faces and accepts her hidden history, and Frank comes into his full strength as a son of Mars with a rare shapeshifting gift, though his life remains tied to a scrap of firewood he must protect. They defeat Alcyoneus and hurry south to find Camp Jupiter under siege by the giant Polybotes and an army of monsters. Together with the legion they win the battle, and Percy's memory is fully restored. In honor of their deeds, both Frank and Percy are raised to praetor. As the fighting settles, the Argo II, the Greek warship built by Leo, arrives over Camp Jupiter carrying Jason, Piper, Leo, and Annabeth. Greeks and Romans stand before one another for the first time, uneasy but united by need, for the Doors of Death remain open and Gaea is still rising. Percy and Annabeth are reunited, and the seven demigods of the prophecy must now sail together toward the ancient lands.