On their last weekend together, Megan and Abby Graves become lost in a remote part of the Arizona desert where they are lured to Skull City, an abandoned mine town. But Skull City is anything but abandoned -- and there's no way out. The sisters are now prey, forced to unleash their most primitive instincts in a desperate, fight for survival against unspeakable horrors -- both human and supernatural. Can Megan and Abby unlock the terrifying secrets of Skull City in time to save themselves or will they become the latest in a long line of victims?