A 1952 play by Creator/AgathaChristie adapted from her 1947 radio play, "Three Blind Mice". Since its opening night in London Soho, the play has been running ''continuously''. It holds the world record for longest running show (of ''any'' type) of the modern era.

The plot takes place in a guest house called Monkswell Manor, run by a Mr. and Mrs. Ralston. They've only just inherited the house, close to where Mrs. Ralston grew up, and they're excited about the arrival of their very first guests. On their first night running the guest house, however, the Ralstons and their four odd lodgers are snowed in during a blizzard. The radio announces that a serial killer is on the loose -- one who uses the children's song "Three Blind Mice" as a {{Leitmotif}}. And the more and more time passes, the more and more reason there is to believe that the killer may be inside Monkswell Manor. When one of the guests indeed ends up murdered, suspicion starts falling on anyone and everyone in the manor. Suffice to say, there are a ton of twists which unfold slowly over the entire course of the tale. [[DoNotSpoilThisEnding And that's all we're going to say.]]

!!This work features examples of:
%%* AssholeVictim
%%* AmbiguouslyGay: Christopher Wren and Miss Casewell.
%%* BluffingTheMurderer
* TheButlerDidIt: A theatreland joke tells of a cab driver who, dropping his passengers off outside the theatre showing The Mousetrap and, feeling angry about not getting a tip, yells "The butler did it!" and drives off. [[DontExplainTheJoke The joke relies on you knowing that]] [[AvertedTrope there isn't a butler in the play.]]
* ClosedCircle: By snowstorm and cut phone lines.
%%* ConvictionByContradiction: Deconstructed [[spoiler:and arguably outright denied]].
* CutPhoneLines: Done by the murderer to further isolate the guesthouse from the outside world.
* DoNotSpoilThisEnding: At the end of the play, the audience is asked not to spoil the ending. No film adaptation (or any other adaptation, for that matter) is allowed to be made while the play is still running. Mass market publication of the script is not allowed in the United Kingdom either. Since it's been running for ''sixty years'', it's likely no adaptation will ever see the light of day. As a matter of fact, TVTropes ain't spoiling either. Got that?
** There's a much nastier variation of the joke from TheButlerDidIt above; in it, the cab driver has actually ''seen'' the play, and he yells out the name of the actual culprit while driving off.
** The USSR didn't particularly care about those nasty capitalist rules, and, therefore, produced in 1990 a pretty straightforward movie adaptation.
** Wikipedia, naturally, notes the ending on its page about the play, much to the dismay of the present owner of the play.
** ''Three Blind Mice'' was eventually released as a book, but its foreword proudly announced that it had been banned for decades.
* EveryoneIsASuspect: There is a reason why the tagline for the play in the brochures is, "Suspect Everyone".
* FauxShadow: Virtually every character gets it at some point, always done very well.
%%* FunnyForeigner: Mr. Paravicini
%%* TheLadette: Miss Casewell.
* LongRunner: It has run since its opening, and is in fact the longest running theatrical production ''period.''
* MetaGuy: Paravicini frequently names conventions of the "cosy" crime fiction genre, proving to be quite GenreSavvy. These include highlighting the dangers of not knowing the guests, commenting on the convenience of the isolation of the characters, and asking Trotter not to spoil the "ending" (reveal the murderer), as the last scene/reveal is always the best scene.
* MinimalistCast: Due to the entire play taking place in ''a single room'' in the middle of a snowstorm.
%%* OldDarkHouse
* RunningGag: Early in the play, when a new character arrives at the house, the description of the killer's clothes is given, usually as they take each item off.
* SnowedIn: During the entire play.
%%* SplitPersonality. Hinted at.
* SuspectIsHatless: The radio description of the killer is actually pretty good, except for the fact that it could potentially describe ''every single character in the play''.
* TenLittleMurderVictims: What the characters trapped in the house suspect is going on.
%%* ThisIsReality
%%* UpperClassTwit: Christopher Wren.
* WhatHappenedToTheMouse: Most of the loose ends are tied up by the end of the play, but a few characters are left with their background unexplained.
By the way, the murderer is...[[spoiler:not to be revealed on this wiki.]]