Joan Fontaine was Oscar-nominated as best actress in the previous year for her much better performance opposite Laurence Olivier in "Rebecca", in a role not dissimilar to that in this typical Hitchcock thriller. That she won the Oscar for this portrayal of Cary Grant's wife who anguishes over the possibility that her new husband may be plotting to kill her says as much for the Academy's penchant at the time for sympathy votes as it does for the talented performances which prevented her winning in 1940. In that year, she lost out to Ginger Rogers' magnificent "Kitty Foyle" and was joined in the also-ran stakes by other memorable turns by Katherine Hepburn for "The Philadelphia Story" and Bette Davis in "The Letter". In 1941, she triumphed ahead of Davis's generally-accepted superior performance in "The Little Foxes", Davis herself having already won the prime accolade twice (for "Dangerous" in 1935 and for "Jezebel" three years later). Thus, she becomes a member of that growing band of performers who have received compensation from the Academy for lesser feats in recognition of more worthy and more-critically acclaimed earlier performances. (In recent years, the example of Paul Newman springs to mind, overlooked for his memorable roles in "Cat on a Hot Tin Roof", "The Hustler", "Hud", "Cool Hand Luke", "Absence of Malice" and "The Verdict", but finally rewarded in 1986 for a lower-key but still very effectual turn in "The Color of Money".)
What is perhaps particularly annoying about all this is that, good as her performance is in "Suspicion", Fontaine is not the pivotal focus of the film. That honour must go to Grant for a performance which achieves Hitchcock's objective of prolonging in the viewer the feeling of doubt about his true intentions towards Fontaine, right up to the end of the picture, and thereby enabling the viewer to fully appreciate the conflict of emotions felt by her. Grant was always going to be ideal for the role with his ability to deliver any line of dialogue, whatever the content, whether sincere or fraudulent, endearing or menacing, with that same consistent inimitable style - you can never guess what motives, if any, lie behind his facade, and that uncertainty is the very essence of Hitchcock's suspense and the whole picture.
RKO's front-office boys were uneasy with Hitchcock's original ending and he was forced to re-shoot it before release. However, if the revised denouement does appear to be a cop-out (and I suggest that it does so only to those who are aware on viewing the film that the punch-line had been changed), it matters little as the joy of the picture has in any event been fulfilled by that time.