Inside the Room is a short black and white movie released in 1935 which features both an "impossible crime" puzzle and a very, very early example of the serial killer story in which the culprit sends enigmatic, menacing messages to his intended victims . One of the most interesting aspects of the film is how it originated. The story began life as a short story written by Marten Cumberland towards the start of his career. "The Diary of Death" was an entertaining tale which merited inclusion in Ronald Knox's famous anthology of 1928, Best Detective Stories. Much more recently, I included it in Miraculous Mysteries.
Cumberland turned his plot into a play, which he called Inside the Room, which was produced in 1934. This was in its turn adapted for film, but by the prolific screenwriter Harry Fowler Mear, rather than by Cumberland. In the short story, the detective, Loreto Santos, is a cosmopolitan character, born in Argentina of Spanish parents, and raised in England. In the film, he becomes Pierre Santos, and is played by Austin Trevor, who had already made a name for himself by portraying Hercule Poirot on the screen.
The story begins with the death in poverty of Lilian Hope, once a celebrity stage performer. She'd fallen on hard times, and been deserted by her friends. Embittered, she'd written a vitriolic diary condemning those she blamed for not rescuing her from tragedy. After her death, fragments of the diary are found with the bodies of two murder victims. Who is killing the people that Lilian scapegoated?
Most of the film takes place in a classic country house setting. A former admirer of Lilian's is among the house guests, and after receiving a warning that he is next on the killer' list, his body is duly found in his room, along with an extract from the diary. Santos, needless to say, applies his brilliant mind to the problem and comes up with the solution. It's not a great film, but quite watchable. Overall, though, I prefer Cumberland's original short story.