Her absolutely best film work, IMHO, is in Max Ophul's "The Reckless Moment." It's next to impossible to find. They almost never air it and the only copy I have ever come across was a bootleg on eBay. It's a great little film noir and she and James Mason were superb.
Oh-oh, I had that on tape when it ran as a late-night movie on a local station about a year ago. I started watching it but couldn't quite get into it, and I think I then taped something else over it. I remember it was strange to see Joan Bennet so young ... as with another movie of hers that I caught a few minutes of a week or so ago, I recognized her voice and her movement/stance before realizing it was her. I didn't know the movie was by Ophul.
I wonder how it works that some small local stations have had some of these gems on hand but TCM and AMC don't. I'm thinking in particular of an old favorite I'd give anything to have a copy of, "Return from the Ashes" with Ingrid Thulin (alumna of Bergman films) and Maximilian Schell.
