Les Ruses du diable (1966)

Ginette Chaluzac, who has left Central France for Paris, now works as a seamstress in a modest workshop in the Marais district. Her life is quiet and uneventful until the day when, to her surprise, she receives a letter containing a hundred-franc banknote. The sender, who remains anonymous, renews his gift day after day and Ginette grows accustomed to the situation. Her material situation improves but after a while she starts asking herself questions about the one who sends her the money and his/her intentions. Till obsession. To make it clear in her mind she eventually decides to investigate...