Francoise (Elisabeth Buré) has a husband Jean-Loup (Hubert Géral) who isn’t very intererested in her. But her friend, Marie-Claude (Marianne Aubert), and her husband, Jean-Claude (Guy Royer), enjoy using an apartment with a two-way mirror into the bedroom of the adjoining apartment. There they can have sex and watch other couples and threesomes have sex at the same time.
Marie-Claude synmpathises with her friend’s plight and gives her the key to the apartment. Françoise is reluctant to make full use of the ‘facilities’ at first, but eventually succumbs to the temptation of using it with an insurance man (André Kay), a female neighbour Valerie (Olivia Flores) and Vincent, a long-time frequenter of the apartments (Richard Lemieuvre). While she is with the last, she sees her husband going at it with Cathy Dupré next door. She ends up having a threesome with Vincent and Mathias (Pjotr Stanislas) while her husband has two girls (Eva Muller and Laura May) on the other side of the mirror. She has much better sex with her husband as a result.