The story is set in a nostalgic Vienna around 1900, and is loosely based on a story by Stefan Zweig. At night, a hurried man arrives at his apartment, telling his manservant that he will depart before the morning. This is Stefan Brand (Louis Jourdan), a failed concert pianist, planning to leave Vienna to avoid a duel. His servant hands him a letter, from one of the many women in his life - dissipation was the main reason for his stranded career -, a woman he cannot remember and who is therefore the "unknown woman."
Brand sits down to read the letter and in a long flashback we see the love Lisa Berndle (Joan Fontaine) felt for him: "By the time you read this letter, I may be dead…. If this reaches you, you will know how I became yours when you didn’t know who I was or even that I existed." In other words, Lisa dies, because her existence has been unacknowledged. The film is her posthumous plea for recognition.
There are three major episodes: as a girl, she was Brand's neighbor and dreamed secretly about the famous piano lion; as a young woman, she has a short affair with him and secretly bears his child; as a mature, married woman of high status she finally meets him again and abandons her husband Johann (Marcel Journet) for her youthful memories - only to discover that her philandering hero doesn't remember at all who she is. He has been completely blind to her lifelong love. She has written the letter in the hospital where she is dying of typhus. Brand spends the night reading her letter, instead of fleeing to save his life and in the morning, her husband who as a military man is an excellent marksman, arrives to get satisfaction in a duel.
This film is more straightforwardly melodramatic than Ophuls' later French films, and misses the irony of those works. That may have been due to the climate in the U.S. with its infamous Hays Code - the cynical La Ronde could never have been filmed in Hollywood. After this, Ophuls only made two minor noir films in Hollywood (Caught and The Reckless Moment) before returning to Europe.
That being said, even in Letter from an Unknown Woman Ophuls keeps enough distance from his characters to make a more critical reading of their actions possible, and laugh at the sardonic joke of Lisa taking revenge on Brand from the grave, as it were, for it is her long letter that keeps him from running away from a duel where he will surely be killed!
As Lisa herself says in the film: "The course of our lives can be changed by such little things. So many passing by, each intent on his own problems. So many faces that one might easily have been lost. I know now that nothing happens by chance. Every moment is measured; every step is counted."
My evaluation: 8.5 points out of 10 for the stationary "train ride" at the fairground, where backgrounds are rotated by a bicycle.
Senses of Cinema essay "Ophuls Conducting: Music and Musicality in Letter from an Unknown Woman". Senses of Cinema review of Letter from an Unknown Woman. Filmsite Movie Review. New Yorker article about Ophuls.