Spectators(1984)

Kay and her man, Paul, have become dissatisfied with their sex life. At his insistence, Kay agrees to bring others into their bed, but all he wants to do is watch Kay with the others, then have sex with her afterwards, one-on-one. After a series of couplings, triplings and otherings, Kay finds a new appreciation for her sexuality, and she walks out leaving a clueless Paul wondering what happened.