A seemingly impossible crime. The standard example being that of a murder victim found in a room with only a single door, securely locked from the inside. Can be the basis for a single plot, or an entire show. A well-designed LockedRoomMystery provides pleasure from trying to figure out the puzzle before it is revealed, from moments of dawning realisation, and from a satisfyingly logical solution. A poorly designed LockedRoomMystery only provides a feeling of having been cheated.

Originally from crime fiction, John Dickson Carr being an acknowledged master. It is noteworthy that EdgarAllanPoe's short story ''The Murders in the Rue Morgue'', widely considered to be the first detective story, involves a LockedRoomMystery.

Appears on television in a number of forms. The relatively pure form as a sub-genre of crime television (e.g., ''{{Monk}}, JonathanCreek'') where the puzzle is eventually unravelled by an eccentric protagonist using subtle clues and pure reason.

The part of the show where the solution to the mystery is explained is TheSummation. Common causes include TimeDelayedDeath or a WoundedGazelleGambit.
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'''Examples:'''

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[[folder: Anime and Manga ]]

* Although it is not a crime show, the anime ''{{Spiral}}'' has a number of locked room mysteries that the protagonist must solve, including one literal locked room murder.
* The ''SuzumiyaHaruhi'' two part episode "Remote Island Syndrome" (and the corresponding chapter in one of the light novels) has a fairly brilliantly-executed example of this.
* ''DetectiveConan'' frequently uses these. Mostly, the killer sets up an elaborate trap involving string or melting ice.
** Similarly, ''TheKindaichiCaseFiles'' features one almost every story.
*The [[spoiler:game between Battler and Beatrice]] consists entirely of these in ''UminekoNoNakuKoroNi''.

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[[folder: Comic Books ]]

* ''DonaldDuck'' and especially ''MickeyMouse'' comics occasionally feature rather lame versions, most commonly involving the Phantom Blot, the evil mastermind opposed to Mickey conceived as an amateur or even professional detective. If it seems the crime could only have been committed by a thief who could turn invisible or whatever, that's probably exactly what he did with the help of some gadget. Oh, and there exist a few decent stories as well that actually feature a real mystery of this sort.
* A staple of ''TheMazeAgency'' comic book series.

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[[folder: Film ]]

* To some extent, ''I, Robot'' fits this trope: Dr. Alfred J. Lanning's death looks like an open-and-shut suicide because the door to his room was locked. Spooner, of course, thinks otherwise.
* Lampooned in the movie "Murder by Death", which pretty much makes fun of all fiction crime characters - "Sidney Wang" modeled after "Charlie Chan", "Sam Diamond" modeled after "Sam Spade" - and their methods of baffling their readers.

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[[folder: Literature ]]

* The original locked room mystery is ''The Murders in the Rue Morgue'', by EdgarAllanPoe. The story became the TropeCodifier for later detective murder mysteries.
* The most famous Sherlock Holmes locked room mystery is probably ''The Case Of The Speckled Band''.
* Parodied in the ''{{Discworld}}'' short story "Theatre of Cruelty", in which Vimes's InternalMonologue brings up the complaint that "wizards made locked room mysteries commonplace" (though there are never any actual examples of this happening in the series).
* Happens in the ''FinneganZwake'' series with the man in Finn and Stoppard's storage room (in ''Horizontal Man'') and Professor Freaze in his tent (in ''Worm Tunnel'').
* Intentionally played to the point of absurdity in the second DirkGently novel by DouglasAdams, ''The Long Dark Tea Time of the Soul''. Dirk finds that his newest client, a wealthy man who had hired him as a security guard, had his head severed and placed on an active record machine while awaiting Dirk. Of course, the door to the room was locked from the inside when the scene was initially discovered. The police analyze this as an elaborate suicide done simply to cause trouble.
* Occurs in Jeffrey Deaver's novel ''The Vanished Man'', where the killer is seemingly able to escape from a locked room where one of his victims is found, as well as disappear into a small crowd.
* Played with in Jasper Fforde's ''The Big Over Easy'', a detective story using nursery rhyme characters. "The entire crime-fighting fraternity yesterday bade a tearful farewell to the last 'locked room' mystery at a large banquet held in its honor. The much-loved conceptual chestnut of mystery fiction for over a century had been unwell for many years and was finally discovered dead at 3:15 A.M. last Tuesday."
** Then it turns out that the locked room mystery was murdered...in a locked room.
* In her non-fiction book ''Sex Crimes'', Alice Vachss (wife of crime writer Andrew Vachss) mentions a real life case that she prosecuted, where the accused was locked in his room every night by nuns, and so supposedly could not have commited the rape. In the end the jury decided that any youth in that position would have found a way out of his room long ago.
* Jonhn Dickson Carr, the acknowledged master of this back in the golden age of crime fiction, provided all sorts of different ways to accomplish this. In his book ''The Hollow Man''/''The Three Coffins'', the main character actually gives a lecture on the different ways a locked room mystery can be created.
* Randall Garrett used this trope often in his LordDarcy stories, with the added twist that magic is real in Darcy's world. Magicians naturally become prime suspects in a LockedRoomMystery, yet Lord Darcy often works out a non-magical explanation, thus exonerating some innocent wizard of the crime.
* "Death in the Dawntime", by F. Gwynplaine Macintyre was written specially for ''The Mammoth Book Of Historical Detectives'', and probably has the earliest setting ever for a detective story. It's a Sealed Cave mystery.
**''The Mammoth Book of Historical Whodunnits'' opened with the AncientEgypt-set "The Locked Tomb Mystery" by ElizabethPeters, which is ExactlyWhatItSaysOnTheTin.
* Stieg Larsson's ''Men Who Hate Women'' is about a journalist investigating a forty year old murder mystery which is a LockedRoomMystery on an island.

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[[folder: Live Action TV ]]

* A more diluted form sometimes appears in a PoliceProcedural (e.g., ''{{CSI}}'') where the puzzle is eventually unravelled by an eccentric protagonist using more obvious clues and AppliedPhlebotinum.
* In genre television (e.g., ''TheXFiles''), the puzzle is typically subverted when an eccentric protagonist (AgentMulder), on the basis of flimsy evidence and wild speculation, reveals that a MonsterOfTheWeek did it. In this case the MonsterOfTheWeek is the one using AppliedPhlebotinum in the form of special monster powers.
* ''JonathanCreek'' is a show built around various locked room mysteries and other seemingly impossible crimes and events, such as a woman being seen going to church in her hometown while she was supposed to be in a coma, a murder seemingly being committed by someone who was already dead and a man being witnessed in both Britain and America simultaneously.
* ''{{Monk}}'' doesn't usually have crimes that look totally impossible, just ones that look impossible for Monk's prime suspect to have committed. The prime suspect is always guilty anyway. Some episodes turned this UpToEleven, with one killer who was in outer space at the time of the murder, and still turned out to be guilty, and another where a guy managed to commit murder while ''in a coma''.
* One ''CrossingJordan'' episode involved a man who was writing a book on vampires found dead in a locked room, drained of blood and with fang wounds in his neck. It turned out to be self-inflicted.

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[[folder: Video Games ]]

* The second ''AceAttorney'' has a case where your assistant is locked in an empty room with the victim, a gunshot is heard, and the door is opened to reveal her standing over the corpse with a smoking gun in her hand. Naturally, [[CourtroomAntic it now falls on you to prove her innocent in court]].
** Another case involves a man found dead in the middle of a snow-covered courtyard with only one set of footprints leading to the body... and an eyewitness who saw the killer leave the murder scene by ''flying over the rooftops''.
* An interesting [[InvertedTrope inversion of this trope]] occurs in ''[[TheElderScrolls Elder Scrolls IV: Oblivion]]'' during a side mission; You and five other people are locked into a mansion on the premise that hidden somewhere in the house is a chest full of gold. Whoever finds it gets to keep it. A fun little game between friends, right? But soon, people start turning up dead, one by one, and suspicions fly as to who the killer is. Now, here's the twist; [[spoiler: This is a Dark Brotherhood, a.k.a. Assassin's mission. '''YOU''' are the killer. The other five people are all targets, the mission is to kill them without them knowing you are the killer, and just for giggles, you're holding the only key to the front door.]]
** Oh, yeah, and [[spoiler: there's no gold, either. Well, not for them, anyway.]]
** Unfortunately, it's programmed so badly that [[spoiler: they never notice that you're the murder even if you do it in front of them.]]
* [[InvokedTrope Invoked]] repeatedly in ''UminekoNoNakuKoroNi'', where it forms the core of the argument that the culprit must be the Golden Witch Beatrice instead of a human. Beatrice is [[ShownTheirWork knowledgable about the classics]] and goes to some lengths to rule out the obvious solutions.

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[[folder: Web Resources ]]

* [[http://www.classiccrimefiction.com/ Crime Fiction]] Resource site with locked room bibliographies.
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