The Postman Always Rings Twice-MM

Frank and Cora start to have an affair soon after they meet. Cora is tired of her situation, married to a man she does not love and working at a diner that she wishes to own. She and Frank scheme to murder Nick in order to start a new life together without her losing the diner. Their first attempt at the murder is a failure, but they eventually succeed (likely not with a BB gun).
Thanks to Dollygray for hosting MonoMonday.