Fast paced, sexy and brilliantly written and directed, The 39 Steps is a landmark in the career of Alfred Hitchcock that lays out his distinctive vision, both in terms of story and cinematic technique.
A simple evening at a London music hall turns into a nightmare for Richard Hannay (Robert Donat), when it ends in gunshots, a panicked crowd and a beautiful and mysterious woman who calls herself Annabella Smith (Lucie Mannheim). After a trip back to Hannay's flat, Smith reveals that not only is she a spy, but she is being pursued by enemy agents after uncovering a plot to steal British military secrets. When Smith is murdered in his flat, and Hannay framed for the crime, he has no choice but to go on the run, using the little information Smith and told him to find the secrets and clear his name. With this being a Hitchcock film, we also get a beautiful blond woman to join him for the ride.
The film starts off at a roaring pace and barely stops for breath. Within twenty minutes of screen time Hannay goes from rakish man about town to wanted man on the run. Hitchcock effectively deploys one of his trademark storytelling devices, The MacGuffin. This is an object or person that presents the motivation or goal for a character, in this case the stolen military secrets, and drives the story, without ever overwhelming it, so the audience can enjoy the digressions.
Hitchcock also shows an assured and developed cinematic technique, going far beyond the simple static framing and sluggish editing of some of his contemporaries. He uses the camera lens to manipulate the point of view and knowledge of the audience, mixing suspense and surprises, and throws in simple but effective methods such as quick transition shots showing changes of location help keep the breakneck pace.
All of this is aided by, as you would expect from Hitchcock, a well constructed script, with set ups and pay-offs. The "innocent man caught up in something dangerous" plot was something that Hitchcock had used before in the silent film The Lodger and the original version of The Man Who Knew Too Much and would use again, most notably in North by Northwest. But here is where we see him first trying other tropes and ideas that he would come back to, the sharp witty dialogue, such the icy cool blonde female sidekick, and the chemistry between the two lead actors. It is also a surprisingly, for the time it was released, sexy film, whether in the scene of the two stars handcuffed together on a bed, or the conversation between two ladies underwear salesman on a train.
The story itself does sound absurd, and at one point one character says that Hannay's tale "sounds like a spy story". This is the case with many of Hitchcock's films, but to use this is as a criticism is to miss the point of what a film like this is about. It does sound absurd, but, like somebody trapped in a dream, that is what he has to deal with, an ordinary man in an extraordinary situation.