A Study in Emerald

A Study in Emerald is a Hugo Award-winning short story by Neil Gaiman, essentially an Intercontinuity Crossover between Sherlock Holmes and the works of HP Lovecraft. Written in the style of a classic Holmes pastiche, this story, roughly following the plot of the first Holmes novel A Study in Scarlet, finds a brilliant consulting detective and his new flatmate investigating the gruesome murder of a member of the royal family.

Can be read here for free, in nifty newsprint format. Which we highly recommend you do before proceeding to the trope list, which contains spoilers.

And also just because it's awesome.

"Indeed. I hate to say this, but it is my experience that when a doctor goes to the bad, he is a fouler and darker creature than the worst cut-throat."
 * Alien Blood: Hence why it's a study in emerald.
 * Alternate History: It's revealed in the first few paragraphs that Eldritch Abominations exist and are accepted fact in this version of Victorian Britain, and that's just the beginning.
 * Anti-Hero:  is a Type III
 * Anti-Villain: Or alternatively he's a Type IV
 * Badass Bookworm:
 * Cultured Badass
 * Bad Moon Rising: The narrator mentions in passing that the moon is now red, and has been for centuries. People are used to it now.
 * Big Good: The Old Ones, in the eyes of most of humanity.
 * Bread, Eggs, Milk, Squick: Our protagonists go to see a theatre troupe perform three one-act plays: a wacky Mistaken Identity comedy, a tragic melodrama about a sweet starving waif who sells violets, and a historical epic about the day the Old Ones awoke and conquered humanity. And the audience is equally charmed by all three.
 * Brown Note
 * Continuity Nod: The name Vernet is a nod to a minor line from the Holmes story "The Adventure of the Greek Interpreter."
 * "John (or perhaps James) Watson" is a reference to Arthur Conan Doyle's notorious inability to keep Watson's first name straight. Call it an incontinuity nod.
 * Likewise, there's a similar nod to the text's disagreement about where on his body Watson was injured in Afghanistan. Study in Scarlet placed it on his leg, later stories said his shoulder. In A Study in Emerald
 * Cosmic Horror Story: But of course.
 * Crack Fic: And a glorious one it is.
 * Cthulumanoid: Prince Franz Drogo of Bohemia
 * Humanoid Abomination: Well, he's got a few extra limbs, but he looks far more human than his aunt Victoria.
 * Deadly Doctor:
 * Humanoid Abomination: Well, he's got a few extra limbs, but he looks far more human than his aunt Victoria.
 * Deadly Doctor:


 * This is also either a Continuity Nod or Mythology Gag, in that the line is originally used to describe Dr. Roylott in The Adventure of the Speckled Band: "When a doctor does go wrong he is the first of criminals."
 * Deliberate Values Dissonance: Tentacled horrors running the place? The natural order of things. To do it otherwise would just be silly.
 * Designated Villain: The murderous duo that the protagonists chase. The reader sympathises with their attempts to free humanity by killing the Old Ones.
 * Did You Just Have Tea With Cthulhu: Early in the story, the protagonists are briefed by the Queen who while oddly voiced, speaks English and talks lucidly, and is nice enough to heal the narrator's injury. She seems decent enough if you ignore the strong implication (probably certainty) that she and her relatives like to Mind Rape people every once in a while and will probably wipe out humanity pretty soon.
 * Did You Just Punch Out Cthulhu?: Two men manage to knife to death a Bohemian prince, a sort of Old One half-breed.
 * Did You Just Romance Cthulu: Victoria is not the same same species as Prince Albert in this universe.
 * Eldritch Abomination: The Great Ones, naturally, inclding Queen Victoria, the Black One of Egypt, and the Ancient Goat.
 * Expy: The Great One Parent to a Thousand, of Lovecraft's Mother of a Thousand Young
 * Genius Bonus: Readers who are particularly knowledgable about Sherlock Holmes will.
 * God Save Us From the Queen: Queen Victoria. Not that one. She's called Victoria because she conquered Europe centuries ago.
 * Half-Human Hybrid: The royal family is all some fraction Eldritch Abomination.
 * Hot Skitty-On-Wailord Action: Victoria's consort is quite human, while she towers over them.
 * Lovecraft Lite
 * Names to Run Away From Really Fast: The Czar Unanswerable, the Black One of Egypt, Parent to a Thousand.
 * Noble Top Enforcer: Lestrade, the detective, narrator and Prince Albert all seem like decent people.
 * Obliviously Evil: The protagonists and Lestrade.
 * Perspective Flip: Kind of.
 * Royally Screwed-Up: Played for kind of dark humor in that the Queen's relatives seem to be the usual debauched and reckless sort that the human Victoria had (and probably many/most monarchs have), but it's taken Up to Eleven, given what they are.
 * Serial Numbers Filed Off (In-Universe): The play they see concerning the girl who sells violets is The Little Match Girl by Hans Christian Andersen with a few details changed.
 * Sherlock Scan: Mostly played straight with the Great Detective, but subverted/parodied in the scene where he recognises that the murder victim is a member of the German royal family... by the number of his limbs and the green shade of his blood.
 * Shout-Out: In the advertisements between chapters. Exsanguinations by Vlad Tepes, anyone?
 * Staring Down Cthulhu: The consulting detective, when he meets Victoria, doesn't seem at all intimidated.
 * That's What I Would Do: The detective tells the narrator that he figured out how the murderers got away based on the fact that he would have done the same thing.
 * Title Drop: When describes the crime scene.
 * Twice-Told Tale: The ending can be hard to follow unless you're relatively familiar with the Sherlock Holmes canon. (The story doesn't require a similarly close knowledge of the Cthulhu mythos, but it doesn't hurt.)
 * The Watson: Well, it's a Sherlock Holmes pastiche, after all.
 * Worthy Opponent: The Great Detective and his equally clever antagonist take this attitude toward each other.
 * Twice-Told Tale: The ending can be hard to follow unless you're relatively familiar with the Sherlock Holmes canon. (The story doesn't require a similarly close knowledge of the Cthulhu mythos, but it doesn't hurt.)
 * The Watson: Well, it's a Sherlock Holmes pastiche, after all.
 * Worthy Opponent: The Great Detective and his equally clever antagonist take this attitude toward each other.