Apollo's journey takes him to Camp Jupiter in the San Francisco Bay area, where the Roman demigods are preparing for a desperate last stand against the evil triumvirate of Roman emperors.

Cast down from Olympus and transformed into a human after angering Zeus, a weak and disoriented Apollo arrives in New York City as a regular teen and is forced to survive in the modern world while endeavoring to regain Zeus' favor.

After learning that he is the son of a mortal woman and Poseidon, god of the sea, twelve-year-old Percy is sent to a summer camp for demigods like himself, and joins his new friends on a quest to prevent a war between the gods. Percy padece dislexia y dificultades para concentrarse. Objeto de burlas por inventarse historias fantásticas, ni siquiera él mismo acaba de creérselas hasta el día que los dioses del Olimpo le revelan la verdad.