Here is the actual tagline for this movie: watch Cary Grant and Grace Kelly be charming in the French Riviera. That's really all you need to know about the film: it is soulless and a little predictable but you get to see two people to whom you are likely quite endeared be charmed with one another.
I sound like I did not like this movie; I in fact liked it quite a bit. It is certainly Hitchcock, though not Hitchcockian; the drama unfolding feels something more akin to that of The Thin Man ↗ or even Ocean's Eleven ↗, where the central plot is less of a primary concern whose resolution brings thought and satisfaction and more of an at-times-flimsy vehicle to chaffeur our two leads from one very pleasant set-piece to another.
And on those grounds, it was marvelous! This is not a Sunday night film, so to speak: it's meant to be watched on a lazy Wednesday, in between bites of pizza or sips of a Kingston Negroni. It's a fun time that is not trying very hard and does not expect you to be, either.