The Stranger on the Third Floor reference article from the English Wikipedia on 24-Apr-2004
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Stranger on the Third Floor

Stranger on the Third Floor is a 1940 film noir. Director - Boris Ingster, Screenplay - Frank Partos, Producer - Lee Marcus, Photography (b&w) - Nicholas Musuraca, Music - Roy Webb, Special Effects - Vernon L. Walker, Art Direction - Van Nest Polglase. Production Company - RKO Radio Pictures.

Cast: John McGuire (Michael Ward), Margaret Tallichet (Jane), Peter Lorre (The Stranger), Elisha Cook Jr (Briggs), Charles Halton (Albert Meng), Ethel Griffies (Mrs Kane), Oscar O’Shea (The Judge).

Plot: Reporter Michael Ward is the key witness in a murder trial. His evidence - that he saw the accused Briggs standing over the body of a man in a diner - is instrumental in having Briggs deemed guilty. But afterwards Ward’s fiancee Jane is worried whether Ward was correct in what he saw and Ward becomes haunted by this question. Next Ward’s neighbour is killed the same way as the man in the diner. But Ward is arrested for trying to point this out to the police. And so Jane goes out to try and clear Ward by finding the sinister stranger that Ward saw on the stairwell.