Mrs. Stone's Thing 1970

Directed by Joseph F. Robertson

A housewife wonders why her husband spends so much time at parties, then is all "sexed out" for days afterwards. She discovers that he's been going to swingers' orgies, and in an attempt to salvage her marriage, persuades him to take her to them. At first she doesn't care for it, but little by little she begins to get into it.