Le corbeau (The Raven) is set in a small town of St Robin which is poisoned by anonymous letters signed by 'The Raven', mostly denounce Dr Germain (Pierre Fresnay. I hope this lead actor showed more emotion. His voice was monotonous, or perhaps it was the bad dubbing.), who commits adultery with Laura Vorzet (Micheline Francey) - wife of the head of psychiatric ward in the town's only hospital - and at the same time has an affair with Denise (Ginette Leclerc), and saves labouring mothers but "kills" the babies. Soon the town is filled with those letters, sent at an amazing speed, 800+ letters in a month, that it is concluded the Raven has nothing to do but composing letters and perhaps the culprit is more than one person.
Things get nasty when Laura's sister Marie Corbin (Héléna Manson) is sent to jail and her house is destroyed by the mob. It's known that Marie Corbin, a nurse, hates Dr Germain because of his sin with her sister. Marie Corbin also dislikes Patient no.13 who complains a lot. Before Marie is arrested, Patient no.13 committed suicide after receiving a letter from The Raven, telling him that his sickness could not be cured and he would be die soon.
Dr Germain, with the help of Laura's husband, Michel Vorzet (Pierre Larquey) does the investigation after the police failed to find the culprit. They summon all the suspects and ask them to write what Dr Vorzet dictates. The theory is, although the real culprit can try to disguise the handwriting, after hours of writing in capital letters, his/her real handwriting will appear. This test is stopped after Denise collaps, exhausted.
The ending has several twists. First, it seems Denise is the culprit; later it turns out Laura is the Raven. Only in the last few minutes, we can really sure about the identity of the Raven. Mother of the Patient No.13, who has sworn to revenge his son's death, carries out her promise.
This work of Henri-Georges Clouzot is not as good as Les Diaboliques, imo. I don't see the reason why Vorzet targets Patient No.13 and Marie Corbin, except he really wants to make Laura suffers. Dr Germain himself doesn't seem to care much until he starts to lose his patients. Vorzet punishes Laura, in the end for her adultery, and in the process by forcing her to write the letters.