The film is a heavily fictionalized treatment of the life of Vincent "Mad Dog" Coll Curran, who was born in 1908 in County Donegal, Ireland.

He is portrayed as a psychopath, incapable of fear or compassion, who is never more happy than when he is recklessly shooting people with his tommy gun or feuding with the fellow mobster Dutch Schultz over whisky hijacking.

The film ends with Coll being shot down by the police after Schultz puts a contract on him, but in fact he was arrested, tried, released, then later killed by associates of Lucky Luciano because he was making too much trouble for the syndicate.

[3] In June, 1961, Monarch Books released a paperback novelization of the screenplay, by Frank Castle, writing under the pseudonym Steve Thurman.

The cover featured a black-and-white still of the movie and an associate standing over the bedroom "rub-out" of a bullet-ridden married couple.