Return from the Ashes (1965)
Hitchcockian thriller based on a French novel. Starts with a bang, as we see a bunch of people on a train, including a little kid messing around the door to the outside. By George, he actually falls out of the moving train, presumably killed. The passengers panic, of course, except for a very haggard-looking woman who shows no emotion. (Ingmar Bergman actress Ingrid Thulin.) The other folks accuse her of having no feelings, until they see the tattooed number on her wrist . . .
Yes, she's a Holocaust survivor, and the time is just after the end of the war. Flashbacks show her starting a romance with a penniless chess player (Maximillian Schell), who is quite obviously a cad. (She's a physician -- a radiologist, to be precise -- and has quite a bit of money.) The same day they get married, the Nazis drag her off.
Back in 1945, she meets her fellow physician friend (Herbert Lom, in a rare Good Guy role) who barely recognizes her. He uses plastic surgery to make her somewhat less haggard, and (for plot reasons, I suppose) she darkens her hair. She seems to want to see her husband without him recognizing her; he, like everybody else, thinks she's dead.
Hubby is fooling around with his wife's stepdaughter from an earlier marriage (Samantha Eggar.) They see her, and think she just looks like his wife. They come up with a wild scheme to have her pretend to be herself (if you see what I mean) so Eggar can inherit her supposedly dead stepmother's wealth. (This all has to do with French law; she can't inherit if there's no proof the stepmother is dead, so they're going to give her one-third of the loot when she goes through the process of impersonating herself.)
No, not the most plausible plot in the world; you have to assume neither of them realize that she's really the stepmother. In one of many plot twists, the whole scheme gets tossed out the window when the stepmother reveals her true identity.
Next, we get a Colombo-style "perfect murder" plot, with an unbreakable alibi and a safe rigged to fire a gun when it's opened. In yet another plot twist, there's a different murder entirely.
Making use of the Holocaust for a thriller may be in questionable taste, but this is quite a good film. The four lead actors are very good. There's a lot of sharp dialogue. A little bit Vertigo and a little bit Diabolique. Recommended.