It's Saturday, and Roland and Corinne Durand are driving from the city to Oinville for the weekend to visit her dying father. They have systematically been poisoning him over several years, to kill him so they can inherit his estate. They believe he will die this weekend and they need to be there to ensure that her mother has not altered the will in her favor. Neither knows that the other is having an affair, and Corinne doesn't know that Roland plans to kill her so he can share the money with his mistress. The happenings over the course of their journey add up to a commentary on their bourgeois values.