Baby Blue(1977)

Marie-Ange ('Baby Blue' - Danièle Troeger) is a student who comes to stay with Jean-Louis Vattier and his wife to do some research. It turns out that this research involves investigating the sex lives of her hosts and their friends. Disappointed with what she discovers, she takes a hand to improve them, taking the husband to visit prostitutes (one of these is Samantha) and making a loan of her boyfriend to the wife. Her 'students' get very enthusiastic - the husband has sex with his secretary (Gwenda Farnel) and the wife seduces her husband's employee. It ends with a wife-swapping foursome with Richard Lemieuvre and Jenny Feeling whose offer of such a party had been turned down at the start of the film.