Henri Savin has managed a trucking company for his lover, Dominique Montlaur, for many years. Now he is planning to leave her for Julie Manet, the woman he has made pregnant, and Dominique is hysterical. She first threatens suicide, then shows up at a meeting of Savin and Julie. Dominique tries everything she can think of to break Savin and Julie apart, to no avail. Frustrated in her efforts, she jumps off a cliff and dies. Savin insists that he and Julie lie to the police about the encounter, although Dominique's death was a suicide and therefore they had no direct hand in it. Detective Waldeck investigates Dominique's death.
