Thrilled to Death (1988)

Cliff, a marginally successful writer of a paperback detective series, has found the perfect setting for murder. He is using an adult club for swingers as a backdrop for his questionable characters to commit their lurid crimes. While reluctantly researching the seedy swing scene, he and his cosmopolitan wife Elaine meet Daryll and Nancy; an outgoing, unusually charming couple. They unwittingly become caught up in a criminal scheme.