The Narrow Margin « Movie from 1952

On a train bound from Chicago to Los Angeles, hard-boiled detective Walter Brown must protect the widow of a gangster who's slated to testify before a grand jury.

Brown's (Charles McCraw) partner was murdered while guarding the ill-tempered Mrs. Neall (Marie Windsor), and the friction between the detective and his charge grows in the confined space.

Now, the mob will stop at nothing to kill Mrs...