Percy Jackson's hope for a normal senior year is shattered as the gods present him with three quests--beginning with the retrieval of Zeus's goblet--in order to get the necessary three letters of recommendation for college.

Uniting with Jason, Piper, and Leo after their dangerous quest, Percy, Hazel, and Frank wonder who will be chosen to fulfill the Prophecy of Seven, completing their group's number, and sail with them to an ancient land to find the mysterious Doors of Death.