Mattie and her husband William lead a secluded life in the forest on the top of a mountain - it seems that they are safely hidden from the whole world. But when Mattie discovers the mutilated corpse of a fox, the young woman realizes that the mountain is not just their home. Someone else appeared in the forest - a monster with sharp fangs and claws, huge and elusive... William believes that this is a demon sent by God to test him. Mattie must not contradict her husband, otherwise she will face problems. But who should she be more afraid of - a monster who appears as if from the underworld, or a man whom she has known all her life?