The film's introduction to Moriarty and his dastardly deeds lays the foundation for a top-tier suspense noir, evoking early Hitch. By the middle of the film, though, it is clear that even with Lupino's help, it can't capitalize on its potential. Its critical flaw is ridding this film world of Holmes' archnemesis with nothing more than a flight of fancy.
As far as Holmes adaptations go, this one is charming and engaging to say the least, and a competently crafted mystery. I can see why Rathbone is such an admired interpretation of the character, as he is a good mix of serious and aloof, though Watson here is a bit too bungling for my taste. Moriarty is interesting, and I like his cruel relationship with his butler. This movie is vintage Hollywood.