I love these short mysteries of variable stakes. The mysteries are varied, and their results each different. Sometimes there's a crime, sometimes a misunderstanding. Sometimes there's a crime and Sherlock lets the criminal go. Sometimes the criminal gets away! There's something eminently entertaining about following Sherlock and Watson through the mysteries, guessing along with them and watching it all unfold. The best ones are the ones where the client is obviously being tricked and yet can't figure out why. 
 Aside rant: These are the episodic mystery capers missing from the modern Sherlock. With only three 90 minute episodes a series, every episode has to be of the highest stakes, and every mystery must have several steps. Rather than demonstrating Sherlock as an accomplished investigator through many mysteries, they simply take it as assumed, and imply that he solves lots of cases through montage sequences. It's an unfortunate restriction of the medium, as I'd take three of these mysteries dramatized over one too-complicated drama executed over an hour and a half.