The Heroes of Olympus: The Lost Hero

Jason Grace awakens on a school bus, unable to remember anything about his past. He is placed next to Piper McLean, his apparent girlfriend and Leo Valdez, his apparent best friend. All three are part of a class field trip to the Grand Canyon, and after they arrive, a classmate turns into a storm spirit and attacks the trio and their trip leader, Coach Gleeson Hedge. In the ensuing fight, Jason battles the spirit and surprises everyone with his powers; Hedge is revealed to be a satyr and is captured by the storm spirit as it flees. A flying chariot with two demigods appear on the scene. The female demigod, Annabeth Chase, expresses her frustration upon seeing that her missing boyfriend, Percy Jackson, is not there as she expected. Jason, Piper, and Leo are told that they are Greek demigods and are taken back to Camp Half-Blood. There, Leo is revealed as a son of Hephaestus, Piper as a daughter of Aphrodite and Jason as a son of Zeus, though Hera tells him he is her champion.

Leo, who has the rare ability to conjure fire, does not use nor tell anyone about it out of guilt about his mother's death seven years prior. Meanwhile, Jason finds out about his sister Thalia Grace, a daughter of Zeus and lieutenant of the Hunters of Artemis. In the woods, Leo discovers a damaged mechanical bronze dragon and rejuvenates it. Shortly thereafter, the three are given a quest to rescue Hera from danger. After encountering Boreas, Piper, Jason, and Leo soon discover that their enemies are working under orders from Gaea, the Greek primordial goddess of the Earth, to overthrow the gods. Throughout their journey, they overcome numerous obstacles and eventually manage to save Coach Hedge. During their quest, they meet Thalia and the Hunters, who have also been looking for Percy. Thalia and Jason have a reunion, the first since Jason was two, but soon get separated on the way to Aelous's castle. After almost being imprisoned by Aeolus under Gaea's orders, the trio manage to escape and end up in San Francisco.

They defeat Enceladus at Mount Diablo and rescue Piper's father, who was being held captive. Jason, Piper and Leo, with the Hunters of Artemis, travel to the Wolf House and defeats the forces of Gaea, saving Hera. They temporarily stall Gaea's plans, but were unable to completely destroy the ancient beings. Meanwhile, at camp, Leo creates plans for a ship that would sail to Greece, and the Hephaestus campers decide to undergo the project, appointing Leo as their new counselor. With part of his memory returned, Jason realizes that he is a son of Jupiter, a hero from a Roman counterpart camp to Camp Half-Blood called Camp Jupiter somewhere near San Francisco, California. Hera, known as Juno to the Romans, has switched him with the Greek hero Percy Jackson, who is now at the Roman camp with no memory of his previous life. Camp Half-Blood and Camp Jupiter always had a ruthless rivalry; whenever they came into contact, things never ended well.