Ingrid Bergman and Cary Grant are rather what I would imagine might have happened if a group of scientists got together and attempted to create in a laboratory setting the two most charismatic people ever. They jump off the screen, and their chemistry together in this film is subtle but intense.
Like, let's talk about the famous kissing scene, which somehow managed to get past the censors. In 1946 when this film was made, the rule was that no kisses on screen could last longer than three seconds. That's it. Period. Because kissing leads to sex, which leads to rock and roll and dancing, and before you know it we're all in that shitty town in Footloose because we can't control ourselves.
Anyway, filmmakers quickly learned that they could easily circumvent this puritanical restriction by using several short kisses rather than one long kiss. So to recap:
One four-second-long kiss = NOT ALLOWED, SINFUL
Ten three-second-long kisses = A-OKAY
So the practical result of this is what we see in Notorious, which is a scene where Grant and Bergman have an extended make-out session (very probably one of the first of its kind) comprising of a series of kisses intermingled with casual conversation. While this is tame by today's standards, we have to note that this was positively steaming in 1946.
And to be fair, Cary Grant and Ingrid Bergman sell it. I am completely convinced that they are in love which each other despite having known each other for a very short time, which makes the plot of this film all the more painful.
You see, Alicia (Bergman) is the daughter of a convicted Nazi collaborator, a man who is tried for treason by the United States and sent to prison. Despite this, she is a patriotic American, and when Devlin (Grant) shows up on her doorstep, it doesn't take a whole lot of convincing for her to agree to travel to South America and assist the American government with keeping an eye on the former Nazis who fled Germany after the war.
That starts out simple enough: she reconnects with some old family friends, gets invited to a few parties, the works. But then an old flame named Alex Sebastian (played by Claude Rains in peak form) turns up, and the plot thickens. You see, Sebastian still has a thing for Alicia, and it's not like she can exactly say, "Hey, I'm not interested in you because I'm secretly in love with my handler and BTW I'm actually a spy."
I mean, at least not on the first few dates, anyway.
And since she's encouraged to lead him on by her superiors, he ends up falling in love with her all over again and eventually proposing. Which creates a little bit of a pickle, as you might imagine.
It's important to note that through all of this, Devlin is being the exact opposite of helpful. He is like the master of sending mixed messages. First, he encourages Alicia to do whatever she can, even dating and eventually marrying Sebastian, to gather intel.
But in practically the same breath, he's also incredibly bitter and jealous that she is seeing another man (on a mission that he sent her on, lest we forget) and basically implies that she's a whore. There's a lot of high and mighty talk about "girls like her" and I do not care for that shit at all.
And really, it's all incredibly uncalled for, because as a secret agent, Alicia is performing remarkably well. In fact, I think that she's one of Ingrid Bergman's most compelling characters. Despite being thrown into one impossible situation after another, she is clever, quick on her feet, and incredibly dedicated to the cause.
I appreciate that Hitchcock didn't feel the need to overload the plot of this film with a complicated spy plot -- he purposefully leaves the mission light and underdeveloped, so that we can be fully engrossed in the tension that unfolds as the film progresses. Although Alicia does her job well, it's only a matter of time before her husband discovers what she's really doing, and begins to plot with his conniving mother to get rid of her.
Most of the film operates as a slow burn, but the last five minutes of the film are like a train rushing towards the conclusion, leaving the audience unsure of how this is all going to play out until the last possible second. It leaves Notorious hitting its climax where most films would be wrapping up into the happily ever after or the downer ending, but its a structural choice that Hitchcock handles well and doesn't unbalance the film.
Aside from Bergman, who turns in one of the best performances of her career, the other two ends of the ersatz love triangle are equally interesting. Cary Grant is required in this role to do the one thing that most filmmakers would never dream of asking him: be un-charming. While he had made a career of playing the smooth talker up to this point, Devlin is a marked departure: he's all rough edges and while you can see why Alicia loves him, it's hard to imagine anyone really liking him.
That's what makes the contrast between him and Sebastian so interesting. In a way, it is showing the difference between a man who is good but not nice, and a man who is nice but not good. Sebastian is a sweet, gentle, doting husband to Alicia -- until he finds out who she really is, then he has no qualms about busting out the poison faster than you can say, "You have an unhealthy attachment to your mother, a theme which will be explored later in Psycho." Meanwhile, Devlin is kind of a dick, but he's also noble, loyal, and brave.
The compelling characterization of the three leads in conjunction with the steady ramp-up of tension that lasts pretty much until the very end of the film creates one of Hitchcock's most effective thrillers. Furthermore, it provides a fascinating look into the political climate and various intrigues at the end of World War II, as the Allied forces scrambled to keep tabs on the Nazis who had either evaded capture or been allowed to resume a relatively normal life. This infuses the narrative with an element of truth that makes it feel more real, and by extension, more intense than some of Hitchcock's more outlandish thrillers.