The graduate wizards of the High Energy Magic building of Unseen University are conducting an experiment in teleportation across worlds, normally accessible only via L-space. With Skazz and Tezz in place as test subjects, the test goes off ''almost'' without a hitch.

Now, the wizards race against time to find out what has happened and fix it. Until then, Lord Havelock Vetinari is trapped in the Victorian London of SherlockHolmes, in the unhappy custody of Dr. Watson, while Holmes finds himself in [[Literature/{{Discworld}} a world of magic and narrative causality]] rather than cold logic.

Fortunately, both worlds have a mystery to investigate. Unfortunately, they will have to be investigated by the dimensionally-displaced Holmes and Vetinari.

Oh, bugger...

The story can be found on [[ fanfiction dot net.]]
!!''The Detective and the Diplomat'' provides examples of the following tropes:

* AllJustADream: Holmes' method of coping with the relative weirdness of Ankh-Morpork is to assume that the whole thing is a fever-dream.
* BeCarefulWhatYouWishFor / BlessedWithSuck: [[spoiler:The cause of the Ankh-Morpork case is a card player from Genua who played Cripple Mr. Onion with [[JerkassGenie a mysterious stranger]], wagering his soul. He won and was granted a wish, and wished to have plenty of money on hand for the rest of his life. Everything he touches now turns to gold. To make things worse, he decided to hide out in Ankh-Morpork.]]
* BewareTheNiceOnes: Ponder, when informed by Holmes that magic is just superstitious rubbish.
* CassandraTruth: Vetinari casually mentions to Watson that he was educated at the Guild of Assassins, leaving Watson wondering whether or not he was kidding. Later events make Watson decide he was ''dead serious''.
* CrackFic: It has Sherlock Holmes in Ankh-Morpork. Enough said.
* DaChief: Vimes, natch.
* DeadpanSnarker
* DogWalksYou: Holmes tries to use Gaspode as a tracking dog to find the perpetrator of the Ankh-Morpork mystery. HilarityEnsues.
* EverythingsBetterWithMonkeys: The Librarian of Unseen University is along for the trip in London. Many Londoners assume he's a trained circus animal; he's not happy about it.
* EverythingsDeaderWithZombies: Reg Shoe patches up Holmes toward the end, much to the shock of the latter.
* ExpectingSomeoneTaller: A few times, directed by those wishing to hire Sherlock Holmes and instead meeting Vetinari masquerading as same.
* {{Fainting}}: Holmes, after witnessing definitive proof that magic works just fine in Ankh-Morpork.
* FishOutOfWater: Vetinari adapts to Victorian London just fine. Holmes in Ankh-Morpork, not so much.
* GilliganCut: When exploring options for entering a warehouse with a heavily barricaded door, Ponder spots some second-story windows...
-->'''Ponder:''' How much do you weigh?\\
'''Holmes:''' ...Why?\\
''(cut to Holmes clinging upside down in sheer terror to the side of the building as he is semi-involuntarily levitated to the second floor)''
* GivingUpOnLogic: Holmes' response when informed that his only eyewitness is a talking dog.
* GroinAttack: Threatened once, and narrowly averted once, but never witnessed.
* HookerWithAHeartOfGold: Roxanne takes pity on Holmes when she discovers that he wanted the ''other'' kind of Seamstress.
* IdenticalStranger: Not quite, but Watson thinks Vetinari will pass.
* ImADoctorNotAPlaceholder:
-->'''Ponder:''' Dammit, Holmes, I'm a wizard, not a runner.
* ItsNotPornItsArt: A student wizard tries to justify cruising London's red light district as anthropology.
* LogicBomb: Holmes arguing with Gaspode over whether the latter can talk.
* OccamsRazor: Played with in Ankh-Morpork. Few things are impossible in the Discworld, and even fewer things are even ''improbable''. This drives Holmes ''absolutely up the wall''.
* OhCrap: A lot.
** Ponder discovering that Lord Vetinari got sent to London by accident.
** Holmes commenting about a "singularly ugly statue"... which turned out to be Detritus.
** The very end.
* OrWasItADream: When Holmes gets back to London, he is still under the impression that the whole trip to Ankh-Morpork was a really vivid dream... until he finds the golden mouse still in his pocket...
* RuleOfFunny: The main reason why Holmes is six inches taller than Vetinari.
* ScrewThisImOuttaHere: After helping Ponder and Holmes locate the cause of the Ankh-Morpork case, Gaspode vanishes when they hear dwarves coming, attracted by the gold. Although he was promised a steak, he isn't feeling suicidal that day.
* SherlockScan: Played with: Holmes pulls a single successful one on Vimes (who resents it), but due to his poor knowledge of the denizens of Ankh-Morpork the entire rest of the day is a comedy of missed deductions.
* ShoutOut
** The last line in the story calls back to the first story in the ''SherlockHolmes'' canon.
** Also, the head of the Confectioners' Guild is identified as [[Literature/CharlieAndTheChocolateFactory Lord Wonka]].
* SlashFic: Not an example here, but clearly Vimes has heard of [[MostFanficWritersAreGirls certain authors]] slashing him with Vetinari.
* SneezeOfDoom: The whole mess starts out from Stibbon sneezing on the last syllable of an incantation.
* SummationGathering: Vetinari calls for one of these in the bombing case.
* SureLetsGoWithThat: After 24 hours without sleep in a magical world, this is roughly Holmes' response when informed that the only intelligble witness to the Ankh-Morpork case is a talking dog.
* TemptingFate: Holmes maintains his lack of belief in magic even when confronted by someone claiming to be a wizard. Holmes demands proof of magic. Ponder is happy to comply.
* UnusualEuphemism: Invoked when Holmes, finding himself in ill-fitting clothing, requests that Vimes fetch him a tailor. Vimes, feeling evil, asks if he would accept a [[HookerWithAHeartOfGold Seamstress]]. Holmes accepts. HilarityEnsues.
* TheWatson: Watson, of course, on the London end, but Ponder fills in on the Ankh-Morpork end of things.
* WeirdnessCensor: Holmes' simply ''doesn't work''.