A remake of the French Le Corbeau ("The Raven"), The Thirteenth Letter is a film noir in a curious setting -- a rural village deep in Quebec, seemingly sleepy and typical. Dr. Laurent (Charles Boyer) returns from a medical convention in Montreal, anxious to see his much younger wife, Cora (Constance Smith). Cora is attracted to Dr. Pearson (Michael Rennie), a young doctor who moved into the town soon after his unfaithful wife killed herself. Soon Pearson, Laurent and Cora all receive letters -- signed "the Raven" -- hinting at an affair between Pearson and Cora. Soon more poison pen letters are showing up around town, including one which insinuates that Pearson has not been telling the truth about the medical condition of a wounded war hero. Distraught, the veteran takes his life, unaware that the information in the letter was a lie. Meanwhile, Pearson has become attracted to Denise, (Linda Darnell), a romance-starved young woman born with a clubfoot. As suspicion builds about who is sending the letters -- and about whether Pearson should be trusted -- the Mayor takes charge of the investigation, and Pearson doubles his efforts to prove his innocence.
~ Craig Butler, All Movie Guide