Jim Dooley’s review published on Letterboxd:
Alfred Hitchcock essentially films Frederick Knott's stage thriller. What is so amazing is how he can take all of the"talkiness" involved in the plotting details and still keep the viewer engaged.
Of course, his secret is to have thoroughly entertaining performers with camera set-ups that immediately hold interest. (He also showed how 3D should be used, heightening the environment rather than being in place as a gimmick.)
Ray Milland is the suave sophisticate, Grace Kelly is wonderfully appealing, Anthony Dawson holds audience empathy as the trap snaps shut, and John Williams is marvelously urbane as the police inspector. Oddly enough, I found little to like in the character played by Robert Cummings although he does a nice job.
The opening is like a Filmmaking 101 course. In just a couple of minutes, Hitchcock covers all we need to know about the love triangle without resorting to 15-minutes of exposition. Indeed, even though this is shot almost entirely in an apartment set, there is such a variety in the set-ups that it is always interesting.
There is a great amount of detail in the murder plotting and the investigation. If you go out for popcorn, you'll miss a key detail. So, there is plenty here for the viewer who likes to keep a murder mystery by the bedside.
The play is very enjoyable and this is an excellent cinematic version of it. I definitely recommend it.