Sibling Rivalry (1990)

Synopsis
Carl Reiner directed this situation comedy about a neglected wife who, in frustration, has her first affair, with humiliating consequences. Kirstie Alley plays Marjorie, the ignored housewife of Harry Turner (Scott Bakula), an obnoxious member of a family of physicians. Marjorie's sister Jeanine (Jami Gertz), sensing her frustration, suggests she have an affair. Marjorie meets a ramrod-handsome man (Sam Elliott) in the check-out line at the local super market. They look into each other's eyes and soon they're having an afternoon of passionate lovemaking. Actually a bit too passionate -- after round five, Marjorie's lover dies from a heart attack. A kind-hearted salesman named Nicholas Meany (Bill Pullman) quickly comes to Marjorie's aid, trying to make the death look like a suicide. Complications compound as Marjorie tries to hide the incident from Harry and his family, but instead she keeps sinking deeper and deeper into a hole of deceit. ~ Paul Brenner, All Movie Guide