Taboo (1979)

Barbara’s husband leaves her after he is disappointed with her. She is left with her son, Paul, and no one else. She is set up on a blind date with a guy who turns out to be a swinger. Her son Paul is having sex with his girlfriend though he is shown to have some Oedipal desires. After Barbara is taken to an orgy, but refuses to participate, she goes home in a heightened state of arousal. In this state, she goes to her sleeping son and seduces him.