AirSabe’s review published on Letterboxd:
Alfred Hitchcock certainly loves murder stories and this just might be one of his best. It is certainly one of the best written with an efficient and thrilling script that doesn't waste a single scene. It makes every little detail important and rewards the audience for paying attention. There are many moving parts with this story, but like a well-oiled machine it all fits together in a satisfying way (when everything comes together I had to fight the urge to snap my fingers and say "Ah-ha!").
Nearly the entire film takes place in one room and thanks to the excellent writing, it manages to stay very suspenseful throughout. The big key to its success is the way the story reinvents itself twice. Things begin like a regular murder movie where we see the plan and its execution. Then the film takes a left turn and turns into more of a thriller. It kept me engaged because now I was remembering each of the details that have been set up to try and figure out what will now be important. Finally, just when it seems the movie has been played out, we get a shift in the POV along with new information that changes everything that comes before.
Although the fascinating plot and tight script are definitely the highlight, the other elements of the film are all great as well (aside from the heavy exposition in the beginning which still serves to set up all the fun to come). Ray Milland is great as the calculating husband and Grace Kelly is equally great as the wife caught in the middle of everything. However, it is John Williams as the the clever and charming chief inspector that leaves the biggest impression. Hitchcock does a nice job making the geography of the room very clear (when characters looked out a window, even though it might not show what is outside, I still knew what they were looking at and the implications of that). Combine all this and you have one of the most thrilling murder thrillers from Hitchcock and a wonderful film in general.