What lies in the mind of the psycho killer? Ed Gein robbed graves to harvest the skin of his victims. Arthur Shawcross strangled prostitutes and ate their remains. Gary Heidink tortured six women in his basement for months. In each case, these killers claimed they were unaware of what's real and what's imagined. What triggered their violence? To understand their atrocities, we will examine the real science of psychosis and meet one of these killers face to face.