Mistress for a Couple (1980)

Georges (Guy Bérardant) is head over heels in love with Claire (Julia Perrin), his lover. Since he still has nice feelings towards his wife (Brigitte) he would like to simply divorce, but she has the money. He decides to ask two killers Max (Joël Charvier) and Edmond (Dominique Aveline)) to do the job. Brigitte, being a gorgeous lady, has no trouble seducing both men and ruling them. So she asks them to kidnap Claire and have some fun with her. They film the scene and show it to the husband. The film ends in the usual orgy where the husband makes friend again with his wife who finally agrees on living with him and his lover.