Spoiler warning!!!
This is probably my least favourite Cary Grant film. I spent most of the time thinking: ignore him, leave him etc. Is he trying to kill her? Should we assume that after the end, when he persuades her to return home with him, that he will kill her after all? I see from checking in a couple of books that this is a reading that some viewers/critics have taken. Finishing early is after all a more reasonable way to film a book, than to change the ending - and this is a more unreasonable change of ending than, for example, in Altman's The Long Goodbye. Unlike Hitchcock's earlier example of making the murderer not the murderer because a star has been cast (when Gosford Park refers to The Lodger, Ivor Novello's murderous habits are not mentioned) the book's ending is not definitely ruled out.
In Robin Wood's Hitchcock's Films Revisited, he writes: "As one mentally 'swiches' from ending to ending , the significance of every scene changes, the apparent solidity of the narrative dissolves, the illusion of the fiction's 'reality' disintegrates, the film becomes a 'modernist' text in which the process of narrative is foregrounded." I enjoy playing intellectual interpretation games as much as anyone else, but unless the film stands on a straightforward reading, then it fails. This one fails. Even after considering the fatal glasses of milk that recur in a few Hitchcock films.
An annoying quibble. The year is 1941. Nothing in the film says that it is set in the past. Beaky (Nigel Bruce) keeps his money in a Paris Bank, and goes there to do financial business? Does he not know that there is a war on? Indeed, were there still any flights from Croydon airport? Is he on good terms with the Nazis? How come it is never suggested that the Germans shot him as a spy or something.
A curiosity. When Johnnie and Lina have dinner with Isobel, the mystery writer, and her brother, the pathologist, there is a fifth person present, who is never explained nor introduced - a woman in a tuxedo. The credits say that she is Nondas Metcalf playing Phyllis Swinghurst. Is this not an example of how lesbians were coded in '40s films? Are we to take her as Isobel's lover? The books that discuss overt and hidden gays/lesbians in Hitchcock (e.g. Robin Wood again) do not include Phyllis Swinghurst.