Crimson Curtain(1952)

Bertal, a despotic and hated theater director, is assassinated before a performance of Macbeth in which he was to play with Aurélia Nobli, his companion and Ludovic Arn, her lover. The police arrive on the scene and the investigation begins. Suspicion first falls on Sigurd, an old actor who had threatened Bertal. But parallels appear between the characters in the play and the actors who play them.