Based on the unique real-life story, Charles Bronson stars as "Machine Gun" Kelly, a cold blooded sadist. Whose 1930's rampage earned him the title of Public Enemy Number One by the FBI. His homicidal tendencies are linked to his personal sensitivity of his height. Together with his even-loving partner, Flo (Susan Cabot), Kelly decides to crown his criminal achievements with a high-profile kidnapping. Unfortunately Kelly takes too great a gamble and his intended farewell to the criminal world results in his own bloody downfall.