Three teenagers wake into lives they barely understand. Jason has no memory of who he is, yet a girl named Piper insists he is her boyfriend and a wisecracking mechanic named Leo claims to be his best friend. When monsters attack during a school field trip, the trio is swept to Camp Half-Blood, a training ground for demigod children of the Greek gods, where they learn the queen of the gods, Hera, has been imprisoned. The three set out on a quest that carries them across the country, from Nevada to Chicago to a frozen palace in the north and finally to California, racing a deadline before a terrible power awakens. Along the way each demigod uncovers a divine parent and a hidden talent: Jason commands the sky, Piper can bend others to her will through her voice, and Leo bends fire and machinery to his purpose. Behind their enemies stirs Gaea, the primordial earth goddess, who is rousing giants and monsters to overthrow Olympus. As Jason recovers fragments of his past, he begins to suspect his origins lie somewhere stranger than Camp Half-Blood, and that his arrival is part of a much larger design. Told in rotating third-person chapters that follow each hero in turn, the story braids friendship, humor, and mounting danger while setting the stage for a wider conflict between two worlds that have never met.