Just Before Nightfall (1971)

Synopsis
Claude Chabrol, the French filmmaker known for his masterful explorations of crime, suspense, and the darker sides of human nature, directed this drama about a man forced to come to terms with his double life. Charles Masson (Michel Bouquet) is a successful ad man with a loving wife, Helene (Stephane Audran), two children, and a close friendship with his next-door neighbor Francois Tellier (Francois Perier), an architect who designed both of their houses. However, Charles has a secret -- he's been having an affair with Francois's wife Laura (Anna Douking). Charles and Laura share an enthusiasm for sadomasochism, and one night while mock-strangling her during lovemaking, Charles goes too far and kills Laura. At first, Charles seems to get away Scot free -- he's not considered a suspect, and while someone did see him leave the scene of the crime, that person declines to inform the police. But Charles cannot escape his conscience, and he eventually feels compelled to tell both Helene and Francois, neither of whom react with any particular shock or dismay. Juste Avant La Nuit was adapted by Chabrol from a novel of the same name by Edouard Atiyah. ~ Mark Deming, All Movie Guide