Mystery Ranch follows no formula for B westerns. Sure, the hero is undeniably good. There is a girl in trouble. Everyone is dressed like a cowboy. Other than that, Mystery Ranch stands out as an original western. I got the feeling that this movie was intended for a broad audience rather than playing to the kids like those that would later worship Gene Autry, Roy Rogers, and Hopalong Cassidy a few years later. Mystery Ranch is tense most of the time because of a strong villain and his evil henchmen. Those people were more violent than other western villains.
George O'Brien certainly was a strong looking figure of a cowboy. I noticed two different approaches to acting as I watched O'Brien in Mystery Ranch. He looked natural, as if he were not acting, when he was interacting with the male characters. When he had romantic dialogue with Cecilia Parker, O'Brien seemed to be forcing his lines. Maybe it was the script; maybe O'Brien was not as comfortable with the dialogue.
Mystery Ranch is an early sound western. There are no singing cowboys, but the villain, Mr. Steele, plays classical piano. It is this piano music that helps set the mood for the movie and works well with the dark lighting. Shadows were used to great effect in making the movie feel like a horror movie. Charles Middleton played Steele in a way that you could feel the evil emanating from the screen. Steele was a villain that had no weakness. I have not seen an evil character this strong in quite a while, and by strong I mean that the character is truly confident and unrepentant. Steele's manner of dealing with his defeat at the end is quite unusual for a B western, but in the context of the character it is totally understandable.
With just enough humor, great performances by O'Brien and Middleton, and a lot of action, Mystery Ranch is an excellent early western movie.