The 13th Letter (1951)
Directed by Otto Preminger

Film Synopsis

St Marc-sur-Richelieu appears to be an idyllic little town, a haven of peace in the Canadian province of Quebec, but a sudden spate of poison pen letters looks set to end all this.  In one of these vile missives, the wife of the respected Dr Laurent, Cora, is accused of having had an illicit affair with her husband's colleague, Dr Pearson.  In another, an unstable young war veteran Jean-Louis Gauthier is notified that he has an incurable cancer - the poor man is so traumatised by this revelation that he immediately kills himself.

As the hateful letters continue to circulate, spreading fear and mistrust, the whole town is soon gripped by paranoia and suspicion.  Dr Laurent confides in Dr Pearson his fear that the letters are being written by Marie Corbin, a puritanical nurse to whom he was briefly engaged before he married Cora.  But then Dr Pearson begins to look like a possible suspect, on account of his reluctance to disclose the reasons for his unexplained departure from his previous practice in London.  As the town's authorities look into the mystery, it soon becomes apparent that there may be more than one poison pen writer...