The Narrow Margin (1952)

Hardboiled detective Walter Brown (Charles McGraw) is assigned to protect a tough-as-nails gangster’s moll (Marie Windsor) from mobsters who want her silenced. On a train from Chicago to an L.A. grand jury, the flat-foot and the femme fatale fight like cat and dog. Fellow travelers include a woman and her son, several small-time crooks and a shadowy fat man who may be a mob assassin. With its intriguing plot twists, this film is often regarded as the best “B” movie ever made.