<P> The novel opens with Percy Jackson (stricken with amnesia) discovering Camp Jupiter and meeting several Roman demigods . After a prophecy from Mars, he, Frank Zhang, and Hazel Levesque travel to Alaska to stop the rise of the giant Alcyoneus and free the god Thanatos, whom the giant has captured . After successfully completing their mission, the group returns to Camp Jupiter to defend it from yet another giant, Polybotes, and his army . After repelling this invasion, the demigods from Camp Jupiter go to meet the delegation from Camp Half - Blood arriving in the flying ship known as the Argo II . </P> <P> The Mark of Athena, the third book, was released on October 2, 2012 . </P> <P> After the Argo II unintentionally fires on Camp Jupiter, the seven demigods of the "Prophecy of Seven" - Percy Jackson, Annabeth Chase, Hazel Levesque, Frank Zhang, Jason Grace, Piper McLean, and Leo Valdez - rush to escape the angered Roman campers . They travel to Rome following the Mark of Athena, a magical talisman designed to lead children of Athena (like Annabeth) to the missing Athena Parthenos . During their journey, they hear that Nico di Angelo has been captured by the Aloadae, and go to rescue him . Although they successfully free the son of Hades and locate the statue, Annabeth and Percy are pulled into Tartarus and the rest of the group resolves to find some way to save them . </P> <P> The House of Hades, the fourth book, was released on October 8, 2013 . </P>

When do they find percy in the heroes of olympus