What is told repetitively, what is romanticized, what is pure, is the final trick.
Alfred Hitchcock is a great adapter. From books to plays, his adaptation is simply ingenious. And maybe, only because he never lets it lose the essence of where it comes from. What the source is. Which then of course can be argued as both an advantage or a disastrous disadvantage. And Dial M For Murder suffers the same consequences that Rope does. The play is written with very few scenes in mind. Scenes with long conversations in mind and long conversation that swoops in every behind the stage activity occurring both before and after the sequence. It can be a bit cheesy, fortunately it is not here.
And this is how Hitchcock dodges all the social rigmarole that a structure of this film comes with. More than 90% of the film is staged in one set piece only. The hall, the main room, the entrance room of this murderous apartment. So why do we despite knowing all these issues that are about to come, still fall for its topsy turvy script. Only because, Hitchcock frames exactly what the audience is going through. That is why he is still loved. Even decades later, his films are satisfying.
Walking in on the murder mystery film, every audience member appoints itself to be the detective of the case, the film. And what all it, the audience, wants to do is analyse every last detail of that crime scene. And Hitchcock gives them exactly what they want. Split into three acts, the first act is the planning of that crime scene. The second is the crime scene going wrong just as it was planned and was to be narrated to the executioners. And the third is justifying the wrong doers deed. And it is a finale in the sense that we aren’t told how this will go down unlike the previous acts.