Something happened to Iris Hollow and her two older sisters Grey and Vivi when they were children, something they can't quite remember but that left each of them with an identical half-moon scar at the base of their throats. When Grey goes missing under suspicious circumstances, Iris learns just how weird her life can get: horned men start shadowing her, a corpse falls out of her sister's ceiling, and ugly, impossible memories start to twist their way to the forefront of her mind. As Iris retraces Grey's last known footsteps, it becomes apparent that the only way to save her sister is to decipher the mystery of what happened to them as children.