3. The Speckled Band
Arguably the most popular of Doyle's short stories, The Speckled Band has already been referenced in Sherlock, during the first episode of last series: A Scandal in Belgravia. As Holmes fame grows through Watson's blogging, we see some of the successful cases that they have worked on together and that Watson has blogged about, including that of "The Speckled Blonde", in which a blonde woman's corpse is found riddled with puncture wounds. While the allusion to the title is nice (and comes along with many others, like The Geek Interpreter for The Greek Interpreter), it would be a shame if one of the best Holmes stories only received this much reference. Doyle's story is not a mystery in the sense of a whodunnit, it's pretty obvious right from the start who the culprit is, but is a classic "howdunnit" in the form of a locked room mystery. The aggressive and manipulative Dr. Roylott has plenty of motive to murder his stepdaughter Julia Stoner, but how he does it while she is locked in her bedroom and leaves no trace is a greater mystery. Moffat and Gatiss could easily take the set up of the slightly unhinged doctor and his house full of exotic animals (a cheetah and a baboon roam the grounds of this country house like Michael Jackson's Bubbles the Chimp or Siegfried and Roy getting mauled by their tigers) and take it in a different direction from the story's deadly poisonous snake. Way back in A Study in Pink, Moffat took the image of the victim scratching out the word "Rache", which in the novel A Study in Scarlet Holmes reveals as German for revenge, dismissing the theory that it is the unfinished name Rachel. In Moffat's version the revenge angle is waved away as far less likely than the female name. In this way perhaps The Speckled Band could refer, as Holmes initially suspects in the story, to a band meaning a group or gang of people with some kind of speckled insignia.