Densel, deducing the truth, goes for Ann Sinclair. Her door is locked, but he knocks on the next door and Ann's son Tommy opens the door and Densel enters, grabbing Tommy. Densel knocks on the interior door to Ann Sinclair's room and threatens to kill Tommy if she doesn't open her door, which she does. He pushes Tommy away and locks himself in with Ann Sinclair and demands the payoff list. Then Brown and Jennings arrive and Densel is trapped, but he has Ann Sinclair as hostage. Brown uses the reflection from the window of a train on the next track to see into Ann Sinclair's compartment, and he shoots Densel through the door without endangering her, then enters the compartment and finishes him off with more shots. Kemp jumps off the stopped train and heads for accomplices in a car which has been following the train, but they are all quickly arrested. The movie ends with the train arriving in Los Angeles and Brown escorting Ann Sinclair from the train station toward the court house. She chooses to walk with Brown the two blocks straight to testify rather than sneak out under cover. Cast Charles McGraw as Det. Sgt. Walter Brown Marie Windsor as Mrs. Frankie Neall Jacqueline White as Ann Sinclair Peter Virgo as Densel Gordon Gebert as Tommy Sinclair Queenie Leonard as Mrs. Troll David Clarke as Joseph Kemp Don Beddoe as Det. Sgt. Gus Forbes Paul Maxey as Sam Jennings Peter Brocco as Vincent Yost Production The film was based on a story by Martin Goldsmith and Jack Leonard titled "Target". RKO bought it in 1950. Music score The film does not have a music score in the usual meaning of the term: the director substituted actual train sounds in places where music would ordinarily be heard for dramatic effect. However, the film does have music, which is stock music "played" on a passenger's (Marie Windsor's) record player in her compartment. Release Richard Fleischer says that RKO's owner, Howard Hughes, was so taken with the film he considered remaking it with Robert Mitchum and Jane Russell. He eventually decided against it but he did assign Fleischer to reshoot sections of the Mitchum-Russell film, His Kind of Woman, with the screenwriter of Margin, Earl Felton, providing uncredited rewrites for the latter picture. The Narrow Margin release was held up for two years after its completion. Reception Critical