Foreign Mystery Drama

I remember seeing this movie on tv, quite possibly my laptop. It was in color. I feel like it was a foreign language movie. There is a couple who is moving into or is trying to move into this apartment. There is a old man who I think infects himself with something or kills himself or one of the people in the couple. I remember newspaper being put up on the windows.  There is a letter / envelope that is slid under the door. They are all involved in some sort of riddle. ,

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