Someone referred to this as "stagy," and was more correct than perhaps he knew: "The Locked Door" was originally a stage play, and this movie was an adaptation, a good one in my opinion.
C. Gardner Sullivan had been writing scenarios and inter-titles since at least 1912, and is honored among aficionados who know his work from those earliest years of motion pictures.
The four top-billed players were also veterans, except for Barbara Stanwyck who has only one previous credit.
Rod La Rocque had been in movies since at least 1914, and put in 12 more years.
Betty Bronson became a huge star with her seventh role, Peter Pan in the movie of that name, and reportedly was chosen for the part by James M. Barrie, the author, himself.
William Boyd, known here at IMDb as "William 'Stage' Boyd," is the primary reason the Screen Actors Guild usually forbids a member having the same name as another, Harrison Ford being the only exception that comes immediately to my mind.
This particular Boyd was busted on something shameful and the picture of "the other" William Boyd, who later became very famous as Hopalong Cassidy, was published in a newspaper, almost destroying his career.
In this cast there are lots of "withs" who help make this a very good movie, including Mack Swain and Zasu Pitts.
The story is not really a mystery, at least not to us, because we see everything that happens, but it is a drama, with conflict and character change.
I'm reminded of the aphorism that people in small towns buy their local paper not to see who did what, because everyone knows, but to see who gets blamed.
That's the premise of this story, and it's well done, plausible by the standards of its time.
There is also a good point for modern society: Laws against consensual acts, such as gambling or ingestion of certain substances, in this case, alcohol, cause more problems than they solve.
"The Locked Door" is good cinema, especially for anyone who wants to watch the evolution of the art.
