Hitchcock was scared of jails. In this film, the lead female character prefers to be bridled by marriage rather than go to jail. It is an intriguing choice for a character who had earlier stated to her husband "You don't love me. I am something you have caught. Some kind of wild animal you have trapped." Aware of this, the young lady who has so far fooled a lot of rich men and escaped the law, prefers marriage to jail. She is smart, a woman who embezzles her employers to buy rich gifts for her mother, aware of modesty in dress (keeps pulling her skirt over her knees) and a convincing liar. Like Hitchcock's Notorious, the marriage in this film is one of convenience, or so it appears—the end of the film is open-ended.
Hitchcock fired the initial scriptwriter (a male), who honestly felt the rape of the wife by the husband was out character with male lead played by Sean Connery. The replaced scriptwriter (a lady) wrote the sequence which was used, in a suggestive way rather than a graphic way. Hitchcock loved to slip in sex even if it was out of character.
Lesbianism is suggested by the husband's sister-in-law's remark "What a dish!" a remark one would associate from the opposite sex. (Hitchcock similarly played with homosexuality in Rope). A critical scene that could be mistaken for child molestation was probably an innocent gesture mistaken by the mother.
Hitchcock usually was attentive to visuals and sound. This is an unusual film where the director swings from one extreme of high sophistication to absolute stupidity. The opening shots of the woman walking away with the yellow handbag are stunning. The silent "cleaning" of the office safe, while a deaf woman cleans the office is simply outstanding. Yet the crass painting of a dock near Marnie's mother's house would make a school kid laugh out loud.
Why would a woman who is scared of red wear red lipstick or not react when her husband's sister-in-law wears red at a party? Similarly, the shot of Marnie's hand not being able to pick up the money in the safe is an unconvincing shot, if ever there was one.
The film can be appreciated and be equally dismissed. The acting by all the main characters was good but Louise Latham performance (and make up!) needs to be singled out for praise. Director Stanley Kubrick seems to have copied Hitchcock's Marnie's differing voice patterns in the young child's voice in his film The Shining.
I am not surprised if people swing from loving the film Marnie to trashing it, and back again. It has memorable elements and elements best forgotten. During the much discussed rape scene, half the faces of both actors are in full light and the other in darkness--cleverly suggesting the duality of character in both individuals. Yet the bottom line is--the film entertains! And it makes you think!