Zebra Lounge (2001)

Alan and Wendy Barnet, a quiet, upper-middle-class yuppie couple, are stuck in rut romantically. After some soul-searching, they decide to spice up their sex life by placing an ad in a swingers magazine. From among the many replies they receive, they arrange a date with Jack and Louise Bauer, a young couple who seem similar to the Barnets. After a very enoyable evening of spouse-swapping, the Barnets feel they've broken out of their rut and are ready to return to a life of monogamy. The Bauers, unfortunately, aren't quite so ready to let go.