The world has fallen in the face of demons spilling out across the Earth from the Hellmouth, a portal that ripped its way into the central United States. Angels with fearsome spirit animals descended from Heaven to wage war, but humanity has been caught in the crossfire. Nathan and Jeremy Sanders, along with a small band of refugees, are just trying to survive in the eastern woods of Texas, aided by a fallen angel named Ash.
But they're about to be drawn into the conflict when demons come looking for Nathan, claiming he's marked to help them raise Lucifer. With the Devil inbound, Nathan, Jeremy, and Ash set off on a quest to retrieve a lost key that could close the Hellmouth, and Nathan discovers he may not be so helpless in the face of such cosmic forces. If he can learn to wield an angelic power unwittingly bestowed upon him, humanity might just have a chance-and a champion.