Suspicion is a rather alarming title for a rather light flick from the master of suspense. I'm guessing it was conjured by RKO Pictures' marketeers to capitalize on Hitchcock's record of thrillers. A fast talking Cary Grant, mesmerizes Joan Fontaine and despite protests from her father, she goes on to marry Cary. Cary plays Johnnie Aysgarth as a flippant trickster who repeatedly causes Tina McLaidlaw (Joan Fontaine) to doubt his intentions. Then he reels her back in with an act that indicates that he has changed. Tina vacillates between trust and distrust till she finally dispels her suspicion.
The book from which the screenplay was adapted, was apparently much darker and ends with the Johnnie character killing Tina. The DVD also had an alternate ending fashioned by Hitchcock that showed this. The movie would have been much better had it ended that way. This is yet another case of the studio meddling with the director's true intentions. Despite being unaware of this while watching the movie, I never thought Cary Grant looked menacing enough. He plays Johnnie with much levity and lacks the smarminess that can convince us of his darker intentions. Coming out only a year after Rebecca, Joan Fontaine is asked to play a mature woman compared to the subservient nameless girl and does well. IMDB says that this was hers was the only Oscar winning performance that Hitchcock directed.