The Mad Thing characterizes that most uncommon of all slayers, the female serial killer. A self-appointed vigilante roams the streets of Los Angeles at night, hunting, killing and mutilating men who have but one tortured behavior in common. Jon Sadler, a profiling for long-time friend, Larry Radino of the Los Angeles Police Department, discovers a common denominator between the victims buried deep within the voluminous files of LA's largest bureaucracy, the Los Angeles Department of Children's Services. In a bizarre turn of events, Jon discovers the identity of the killer, but is compelled to withhold the identification.