Constance aux enfers (1964)

Rear Window meets Estate violenta. The middle-aged Constance watches a young couple that lives across the courtyard; the girl plays loud pop music and goes out of her way to be unpleasant to the classically educated and piano-playing Constance. Then one day Constance sees the boyfriend strangle the little tart in a fit of jealousy. He sees her, too, and has nobody else to turn to for help. Constance keeps silent about the murder and offers the young Hugo a place in her bed. Then the blackmail notes start to arrive...