Blood Simple

Blood Simple is a 1984 American neonoir psychological crime thriller film written, edited, produced and directed by Joel and Ethan Coen. It was the directorial debut of the Coens and the first major film of cinematographer Barry Sonnenfeld, who later became a noted director, as well as the feature film debut of Joel Coens wife Frances McDormand, who subsequently starred in many of his features.

The movie opens with a short voiceover monologue between Abby Frances McDormand and Ray John Getz in a car. This monologue happens before we know whats happening between them. Instead of driving Abby to Houston he drives to a motel and they have sex. We later find out that Julian Marty Dan Hedaya, who owns a bar in the rural countryside of Texas, suspects Abbys affair with Ray, who happens to be one of his bartenders. She protects herself with a revolver and three bullets.Marty though has suspected for a while so he hires private detective Loren Visser M. Emmet Walsh to take photos of Ray and Abby. Visser photographs them in the act and phones them while they are in the motel room, but remains silent. ........

Source: Wikipedia