The title character of L'Etrange Monsieur Victor is a seemingly respectable storekeeper, happily married to the lovely Madeleine. As the film opens, Victor and Madeleine have just become the proud parents of an adorable baby boy. Everything seems perfect for Victor, a man admired for his good works and love of children. But Victor has a secret life; he is leader of a criminal gang. Now that he is a father, he decides to leave behind his life of crime, but one member of his gang doesn't like this and threatens to expose him. Almost without thinking, Victor kills the man. He escapes suspicion, however, and an innocent man named Bastien is sent to prison instead. As time passes, Victor becomes overcome with guilt and remorse; he loses his temper easily and is likewise easily agitated. Eventually Bastien escapes, and Victor takes him in and hides him -- but doing so threatens to bring about the truth about the murder.