The Sign of Four by Arthur Conan Doyle Published: 1890 This is the second of four Sherlock Holmes novels. The only one I’d read previously was the third, The Hound of the Baskervilles, so it appears I’ll be reading these in the most bizarre order I can manage. This does make a few references to A Study in Scarlet, I believe, but it doesn’t seem like the order in the series matters all that much. After annually receiving a mysterious and incredibly valuable pearl in the mail for the past six years, Mary Morstan was delivered a letter asking her to finally meet the unknown sender. He had some information…