The 13th Letter (1951)

A Strange Kind of Killer Is Loose in This Town!

When Dr. Pearson comes to a quiet Quebec town to set up his medical practice, he attracts the notice of Cora, whose husband, Paul, is the town's other doctor, and Denise, eldest daughter of the family in whose house he lodges. When an unknown person begins writing letters attacking Dr. Pearson and Cora for having an affair, a complex web of rumors, lies and accusations begins to ensnare nearly everyone in town.