Le bouche-trou (1976)

François and Joelle are lovers, and take great pleasure in their sexual embraces. But François is a cameraman that puts his work at a higher priority. One night, when they are interrupted by a phone call from his work, and leaves in a hurry with his camera and three shirts, Joelle can't wait all those shirts to be dirty before she is sexually satiated. Therefore, she goes out searching, and finding, a number of liaisons with men and women alike. On one of her outings, she happens to see François having an affair with a man. It seems that she doesn't reject the idea of joining with him again - in a menage-a-trois.