After receiving a mysterious mask, Ellen Morris believes she was attacked by an evil being she calls "Nightmare Man." Her husband, Bill, believes she is crazy. On their way to the mental hospital their car breaks down and Bill goes to get gas, leaving Ellen alone. When Nightmare Man appears, Ellen takes off into the woods, unsure whether she is hallucinating or not. She stumbles upon a cabin filled with friends who unknowingly becoming prey the moment Ellen steps inside.