Rick Riordan’s 2010 YA novel, The Lost Hero, tells the story of three demigods: Jason Grace, son of Jupiter/Zeus; Piper McClean, daughter of Aphrodite; and Leo Valdez, son of Hephaestus. The book alternates between narrating these three characters’ thoughts and experiences in free indirect discourse. Each has a distinctive style: Jason is vaguely confused, but aware of others’ high expectations; Piper is lovelorn over Jason, and self-pitying because her father’s fame has weakened their bond; and Leo hides his vulnerability and pain over his mother’s death with humor. Together, they journey from Nevada to Maine to California to free the goddess Hera from captivity. In the process, each discovers his or her own strength.

Other works by this author include The Tower of Nero, The Chalice of the Gods, and Daughter of the Deep.

At the beginning of the narrative, Jason has lost all of his memories and does not even know his last name. He wakes up on a bus holding Piper’s hand. He is sure he wasn’t there a moment before and confused as he learns that she believes she is his girlfriend. Likewise, the boy in front of them, Leo, believes he is Jason’s best friend. The two tell him that they’re all problematic teenagers who were sent to the Wilderness School for reformation. Only their supervisor, Coach Hedge, can confirm that he’s never seen Jason before.

The mystery of Jason’s identity is partially unraveled when a group of venti, or storm spirits, attack the campers. Jason fights them off and rescues Piper from death, in the process displaying his ability to fly. Coach Hedge is taken by a ventus, but soon, teenage demigods Annabeth and Butch arrive on winged horses and take Jason, Leo, and Piper to Camp Half-Blood. They are disappointed to find these three rather than their missing friend Percy Jackson, a son of Neptune. The camp has suffered much loss recently, due to a war with the Titans.

At Camp Half-Blood, Leo discovers he is a son of Hephaestus, and Piper learns she is a daughter of Aphrodite. These identities explain long-standing questions and problems in their lives. Leo was, as a child, exposed to fire by his “Tia Callida,” and eventually learned he could create fire on his own, a skill he stopped using after his mother’s death by fire. Furthermore, Hephaestus’s status as god of the forge parallels Leo’s own skill with invention. Likewise, Piper has always been able to persuade people into giving her things—most recently, a BMW. When the employee accused her of theft, Piper’s father, Tristan, sent her to the Wilderness School. She learns that charmspeak is a gift from Aphrodite. Both struggle to make sense of this new information, which is further complicated by Leo’s visions of his Tia Callida and Piper’s visitation by a strange voice that keeps telling her she must betray her friends to save her father.

As Jason, Piper, and Leo compare notes on their visions and visitations with Chiron, the camp’s centaur overseer, they realize that Hera is imprisoned, and is calling on Jason to save her. She has taken his memories, supposedly for his own protection. She does not reveal the identity of her captor.

When the campers gather around the campfire, Chiron reveals that Jason was claimed long ago. He then announces himself as the son of Jupiter, using his father’s Roman name rather than Greek. Then, the mortal oracle Rachel Dare reveals that the Great Prophecy has begun: a group of seven demigods must band together to save the world. She expands on the prophecy, noting that Jason must go with a “dove” and a “forge” to save Hera. This seems to refer to Leo and Piper. They need transportation to begin their journey, so Leo uses his engineering skills to repair an errant bronze dragon that he names Festus.

The three begin their journey at the home of Boreus, god of the North Wind, where they meet his daughter Khino, the goddess of snow. Boreus has instructions from Aeolus, the god of Wind, to kill all demigods on sight—but he lets them go (a decision which Khino opposes) on the condition that they capture the venti and deliver them to Aeolus.

They proceed on their journey to Aeolus, and on the way, they stop several times, twice because Festus breaks down. At each stop, the demigods face a difficult obstacle. First, Leo saves Jason and Piper from three Cyclopes; then, Piper saves Jason and Leo from Medea, the mortal villain come back to life. Finally, Jason saves his friends from King Midas, also resurrected by someone he calls “his patron.” The three bond closely (with Piper and Jason experiencing strong romantic attraction to one another), but Piper remains torn, as she knows the giant Enceladus has her father. She debates over betraying her friends, but after the encounter with King Midas, tells them the truth.

When they retrieve the venti from Medea, the demigods also retrieve Coach Hedge. After escaping King Midas, the demigods are confronted by wolves, but saved by the Artemis Hunters and Jason’s sister, Thalia Grace. She and her brother reunite, and she escorts them to Aeolus’s floating fortress. Aeolus seems inclined to help the demigods until a mysterious female voice convinces him otherwise. He expels them by an air chute, but Aphrodite rescues the demigods, and in the process tells Piper that their true enemy is Gaea, mother earth herself. She is awakening long-dead mortals, giants, and monsters that seek to defeat the gods.

Together, and with an assist from Zeus, the demigods defeat Enceladus and rescue Tristan. Coach Hedge offers to care for him as the demigods complete their quest. Finally, they arrive in the San Francisco Bay Area at Wolf House, and reunite with the Artemis Hunters, who are battling ogres and snow spirits. Khione reappears, revealing that she imprisoned Hera to assist Gaea and claim her rightful place in the world order.

Leo and Piper work together to free Hera as Jason battles the giant Porphyrion. At the final moment, Hera is freed, and uses her full power to scare away the giant. Jason almost dies, but Piper is able to bring him back with charmspeak. Hera returns the demigods to Camp Half-Blood.

At Camp Half-Blood, each character arrives more empowered. However, they also know there is more battle in store. It is finally clear that there are two groups of demigods, Greek and Roman. Hera took Jason’s memories so he would forget his Roman identity and forge bonds with the Greeks. Now, the seven greatest Greek and Roman demigods must band together to defeat a common enemy. The first step is finding Percy Jackson, who Jason assumes was sent to the Roman camp in his stead.