<P> Quickly befriending the guards, Frank Zhang, son of Mars; and Hazel Levesque, daughter of Pluto, and subsequently gets introduced to the praetor of the camp, Reyna, and the augur Octavian, who quickly takes a dislike to Percy . Being outcasts themselves at Camp Jupiter, Frank and Hazel relate to Percy's outsider status and consider it their duty to help him adjust and acclimate quickly to Camp Jupiter's routines and leadership . Before any of them have a chance to gain their footing, they are selected to go on a quest to rescue Thanatos, the god of death, from the Giant Alcyoneus who is hiding deep in Alaska after receiving a direct prophecy from Mars, the Roman god of war: </P> <P> Go to Alaska . Find Thanatos and free him . Come back by sundown on June twenty - fourth or die . </P> <P> On their journey, they encounter Phineas, the blind human who helped Jason, leader of the Argonauts on his journey, and befriend a harpy named Ella that supposedly torments him . They also see the three Cyclopes that Jason Grace, Piper McLean, and Leo Valdez encountered in The Lost Hero . During the trip, the trio learns that the goddess Gaea is awakening from several millennia of slumber with a plan to destroy the gods and the world along with them . Her seven Giant children are being woken, each of whom is matched to fight their counterpart god . Each Giant has the skills to oppose one god and they can only be defeated if the gods and the demigods join forces . This proves to be difficult . Percy and his friends manage to defeat the Alaskan Giant and save Camp Jupiter from destruction . During their journey, Hazel and Frank become true heroes who know how to use their powers and have self - confidence . Percy regains his memory on their return to Camp Jupiter and finds an army of monsters (including Stheno, Euryale, and the three Cyclopes) led by Polybotes attacking it . Percy successfully defeats him with the help of Terminus, his Cyclops half - brother, Tyson and the hellhound, Mrs. O'Leary . At the end of the book, the Greek airship, Argo II arrives setting up the plot for The Mark of Athena . </P> <Ul> <Li> Percy Jackson: A demigod son of Poseidon (Neptune), who is the main protagonist in the first Camp Half - Blood series . He and Jason Grace have been swapped, because Hera (Juno in Roman form) has wiped their memories away to unite the two demigod camps . Percy is sent from Camp Half - Blood to Camp Jupiter, Jason's home . He goes on a quest with Frank Zhang, son of Mars, and Hazel Levesque, daughter of Pluto, to save Thanatos, Pluto's lieutenant and the deity of death . He succeeds and at the end of the book leads the Roman camp into battle against Gaea's forces and is made praetor by the campers . His memories are restored at around the middle of the book, as Percy drinks gorgon's blood when he challenges Phineas . </Li> <Li> Hazel Levesque: daughter of Pluto and Nico's half sister . She has been recently resurrected by Nico from her death in 1942 at the age of 13 and lives in Camp Jupiter . She has a crush on Frank Zhang . She is an African American demigod from New Orleans . </Li> <Li> Frank Zhang: a son of Mars and a legacy (distant descendant) of Poseidon on his mother's side . A notable ancestor of Frank is Periclymenus, who was given the ability of shapeshifting by his grandfather, Poseidon . It is revealed that the descendants of Periclymenus have inherited this ability, and Frank learns to use it late in the novel . Frank is a Roman demigod at Camp Jupiter, a camp for Roman demigods . Frank has a crush on Hazel, which she reciprocates . He is a Chinese Canadian . </Li> </Ul>

When does percy get his memory back in the son of neptune