Kristin and her friend Kelly, are Lessers, the lowest part of society. They live at Hyperion Academy and work in the fields to provide food to Mid Olympus, the big city which is the center of everything.
When Kristin hears about the Unity, a rebellious group, which is visiting the Blood Fountain, she needs to know why they're there.
She learns that they're there looking for the Omen, a creature said to be born from Tartarus itself. They search for it because it's a way to overthrow the tyranic gods.
But what they find is not what they would have expected.