One does not die that way (1946)

In the studio where the famous director Eric Von Berg reigns, Pierre Vanier, the male star of the film and the lover of Berg's muse, dies while rehearsing a scene. Over the course of a tangled investigation, the culprit is unmasked. This honest dresser is the adoptive mother of Vanier's wife, too unhappy with such a husband. The inspector, moved, concludes a suicide.