While not as compelling as Hitchcock's 1954 adaptation when it comes to cinematic technique, Christopher Plummer's turn as the socipathic but suave Tony Wendice makes this made-for-TV version of the perennial thriller classic DIAL M FOR MURDER worth a watch. It's not exactly a filmed stage play, but it's a hair away from being as such. It does try to "open up" the play by setting Margot and Max's conversation at a movie studio filming an adaptation of one of the latter's mystery novels rather than in the Wendice apartment, which I thought was a clever touch, playing upon the subtle meta elements of the original play.
As for the story itself, it's pretty much exactly the original play and/or the Hitchcock movie (which was adapted by the play's author Frederick Knott anyhow). I personally think the play's first half is more interesting than the second, since none of the other characters can match Tony for charisma or guile. But it is clever and twisty, and therefore enjoyable.