This is a good entry in the Arthur Wontner series of Sherlock Holmes movies, adapting one of Arthur Conan Doyle's most interesting and involved stories. The movie does a solid job of telling the story within its obvious budgetary constraints, Wontner as usual looks authentic as Holmes, and the story does the rest. Lyn Harding is solid as Moriarty, but as this series tended to do, the character is played more as a tough guy than as a twisted genius of crime.
The original story is a particularly good one because it takes a Holmes mystery with the usual intriguing details and puzzles, and combines it with an elaborate story about the backgrounds of the other characters involved. The original story has rarely been used in the movies, and it was unfortunately one of the ones not included in the outstanding Jeremy Brett series. So it's particularly fortunate that this version of it is still around.
The settings range from an old English castle to a rough part of the USA where outlaws are in charge. It's too bad that the production values were so low, because with some extra work, the settings could really add a lot to the atmosphere. Here, at least, they provide just enough to make a believable backdrop to the interesting story.