It is October of Percy’s senior year of high school. Percy is a demigod, the son of a mortal woman and the sea god Poseidon, and his schedule is packed with classes and tutoring to make up for his lost junior year. He wants to graduate on time to start college at New Rome University in California with his girlfriend, Annabeth, herself the demigod daughter of Athena, the goddess of wisdom. The deadline to apply is approaching, and he still needs two more letters of recommendation from Greek gods.

His English teacher wakes him from a nap in class saying his aunt is waiting in the office. As he has no aunts on the human side of his family, he is concerned, even more so when his school counselor Eudora, a Nereid (sea nymph) who works for his father, Poseidon, hides in her office. Stepping into the principal’s office, he finds a woman dressed in black, green fire wreathing her hair. She dismisses the principal, who appears entranced, and introduces herself as the “Triple Goddess.” Percy acknowledges that he should probably know what that means, but with so many Greek gods and their propensity for changing form, it can be difficult to keep track.