Blood Simple.

The film opens with a short voice-over monologue voiced by M. Emmet Walsh as various images of the Texas landscape are shown. The film then shifts to a conversation between Abby (Frances McDormand) and Ray (John Getz) in a car as it drives through a heavy downpour at night. They seem to be discussing Abby's bad marriage and Ray indicates that he's driving her to Houston. But instead of driving Abby to Houston, Ray drives to a motel and they have sex. We later find out that Abby's husband, Julian Marty (Dan Hedaya), who owns a Texas bar, had hired a private detective (M. Emmet Walsh) to follow Abby. The detective took photos of the tryst and delivered the prints to Marty. Ray turns out to be a bartender working for Marty. Read more on Wikipedia.