Wealthy man, may have killed his wife. Housekeeper/mistress goes out in the fog to mail a letter, he follows, kills her (or so he thought) actually kills another woman (a policeman's wife if I remember).
Housekeeper figures out he was trying to kill her, in the end she poisons him.
I missed some of the beginning of the movie, but the portion I saw was great and would like to watch the whole move.
It was black and white, set in London I think.
