Juste avant la nuit (1971) DVD

This Claude Chabrol film is a dark tale of secrets, erotica, and crime. 

Successful advertising executive Charles Masson is involved in a hot affair with his best friend's wife, Laura. When one of their S&M romps goes bad, Charles strangles Laura to death in an apartment that was borrowed. While racing from the scene of the crime, he bumps into his friend Francois and drives back to their neighborhood. When someone realises that he'd seen Charles and Laura together in the past, he decides not to go to the police with the information. With no clues to the crime, police have a hard time finding a suspect. Charles, however, has an even harder time coping with guilt, his children, and his loyal wife, Helene.