Special Agent Cooper’s review published on Letterboxd:
This is an outstanding mental chess game with several players making moves. It's simply fascinating to watch a nefarious husband (our lead, Ray Milland), his adulterous wife's lover (who happens to be a keen murder novelist) and a veteran inspector all constantly trying to think several steps ahead of one another and constantly adjust their stories and theories after a man is killed in the main character's house. Even though this is not a murder mystery in the traditional sense, because the audience sees the murder play out immediately and has detailed knowledge of the perpetration, this film does an incredible job of making the investigation extremely entertaining to watch play out, as everyone involved is working hard to throw each other for a loop several times over.
Recent mystery phenomenon Knives Out actually benefitted from a similar rarely used take on the murder mystery setup. One wouldn't logically think a murder mystery could be as good if the killer's identity is immediately known, but both filmmakers smartly realized (as Hitchcock ALWAYS does) that the best storytelling always rests within the details. Letting the audience learn new details to recontextualize events and watching the characters uncover these details is supremely entertaining in its own right.
While many of Hitchcock's classic films (except Rear Window, of course) involve some sort of journey or road adventure to a new town, or sometimes international travel, in search of some refuge, pursued person, escape or McGuffin, this is almost entirely a "one room" type of film. It's very easily set to be performed as a play. The film even has an intermission as would a play. A film that has such a static environment could lend itself to boredom, but Dial M has a few things working in its favor to correct that and then some.
Let's talk about visuals, first. Anyone who has seen a handful of Hitchcock films knows that the use of smart visual touches is always completely top tier, regardless of whether we are talking about his very most or very least popular film. While only a couple scenes from this film are as visually breathtaking as compared to top moments from other Hitchcock classics, all of the usual outstanding visual cues for storytelling and character head space are present. Hitchcock puts you in the mind of his characters. A man nervously glances to a potential weapon (that doesn't even materialize as such) as we watch him twitch and momentarily take his first person POV. An important hiding spot for an item is constantly given zoom treatment before and after use. Hitchcock does this sort of thing like no one else before him did and like no one else does to this day.
Okay, so the film looks good. It's a Hitchcock. They all do. Let's talk about this script and Milland's performance, because they never let this story lose steam for a moment. A good deal of the first act of this film really revolves around Milland scheming and explaining his schemes, but he does so with such confidence and charisma that you don't want a miss a word of it. Mind you, his character is a total shitheel and you SHOULDN'T want to share his mindset or thoughts for a minute, but he delivers one of the all-time underrated "subtle villain" performances in this film. He's a master manipulator whose angle is more sly confidence and prepared contingency than pure charm. The film is absolutely throttled and charged by Milland's masterful performance and a brilliant, back-and-forth, mile-a-minute script that never feels like a stretch... and all of this is done while mostly watching a small handful of people discuss one general plot idea in mostly one room for almost 2 hours. Now that's an accomplishment. I should probably mention Grace Kelly, Robert Cummings and John Williams were all as strong as expected in this film too, but this was really Milland's show.
That's nine Hitchcock films now finished and yet another high grade, a rightful classic in my eyes. These are having such an extremely high success rate for my love and really a 100% success rate for a general appreciation, so far.