Lady on a Train (1945)

Director: Charles David
Cast: Allen Jenkins, Dan Duryea, David Bruce, Deanna Durbin, Edward Everett Horton, George Coulouris, Patricia Morison, Ralph Bellamy

Synopsis:

While watching from her train window, Nikki Collins witnesses a murder in a nearby building. When she alerts the police, they think she has read one too many mystery novels. She then enlists a popular mystery writer to help her solve the crime on her own, but her sleuthing attracts the attentions of suitors and killers.