When a plane crashes in the wilderness of the Upper Peninsula, accident investigator Boyd Taylor arrives to find the plane mostly intact and determines that all the passengers should have survived. The problem is they've disappeared. As he delves into the crash with the help of local park ranger Aila McGowan, he uncovers evidence that indicates someone or something chased them off. When bodies begin to appear - killed in ways not humanly possible - they fear a monster called the 'Grey Man' is stalking the surrounding forest and if they don't find a way to stop him, there will be no survivors left to save - including themselves.