The fourth Sherlock Holmes novel and probably the least well known. That said, it’s still a great story and one that may be underrated by fans out there. I’d argue there is more of what makes a good Sherlock Holmes story here than in Hound of the Baskervilles. We certainly see more of Holmes directly involved in the story and solving puzzles than we do in Hound. The story does feature a flashback to explain the current mystery and the continuity of the Holmes canon comes into huge question here with the explanation that Moriarty is behind this, thus making it dubious that Watson has never heard of him later in the chronology. But looking past all of that, the story is a good one and the flashback is well written and entertaining.