Australian Professor Ian Delaney is single-minded in his determination to prove his theory that one can discover the moment that the life force leaves the body. After succumbing to the temptation to kill a girl under scientifically controlled conditions, he takes an offer of work in St Louis, hoping to leave the undiscovered crime behind him. In America, Wayne Richardson seeks revenge by killing his ex-girlfriend, believing it will give him the upper hand, a means to seize control following their breakup. Wayne quickly discovers that he enjoys killing and begins to seek out young women who resemble his dead ex-girlfriend. Ian and Wayne meet and, when Ian recognizes the symptoms of violent delusion, he employs Wayne to help him further his research. Despite the police closing in, the two killers manage to evade identification time and time again as the death toll rises in their wake. The detective in charge of the case, John Barnes, is frantic, willing to try anything to catch his killer. With time running out, he searches desperately for answers before another body is found...or the culprit slips into the woodwork for good.