To kill is one of the greatest crimes against humanity―to kill repeatedly, often accompanied by sexually motivated acts that are also taboo, is beyond comprehension. Why do serial killers and psychopaths do it? What motivates them? Wildly deviant behaviour can sometimes be understood when displayed by a lone madman, but what about the killers who are judged normal, or the ones who act in despicable agreement with another? This book addresses such questions in a compelling examination of many true-life cases featuring the world's most notorious killers.