Elysium, Oklahoma, becomes the playground for the Two Sisters, the goddesses Life and Death, when they decide to enact a ruthless Game--their Dust Soldiers inform the townspeople they have ten years to prove themselves worthy, or else the Dust Soldiers will return and kill everyone. Those ten years are up, and seventeen-year-old Sal Wilkerson is chosen to lead the people--then, when the charming stranger Asa shows up from the outside world, Sal makes a mistake and gets herself and Asa exiled to the outer Desert of Dust and Steel. There, they team up with a group of witches who use their powers to make magic-powered scrap-metal horses to defend Elysium at all costs.