The plot involves the mom working as a maid/cleaning lady/housekeeper for a mysterious boss, who blackmails/persuades her to masturbate and eventually to seduce her son. I remember the boss setting up hitting cameras and knowing what she has done at home with her son. She continues to become more sexual as the story goes on, both at her boss' house and at home. Her boss communicates with her with notes or recordings I can't remember. Maybe it takes place in boston.