Score (1973)

"A Man and a Woman and a Woman and a Man and a Man and a Woman etc., etc."

In the mythical European city of Leisure, married couple Jack and Elvira have an ongoing bet regarding who can seduce whom. This comes up in the wake of a swinging night with a couple of tourists picked up via a newspaper ad. Elvira, a self-professed "sexual snob" has bet she can seduce newlywed Betsy, married to handsome marine biologist Eddie. If she fails by midnight, then Jack gets to seduce Eddie.