History Main / HeKnowsTooMuch

* If you're a character in an Creator/AgathaChristie novel, don't ''ever'' try to blackmail a murderer if you want to live to the end of the novel.
** Amberiotis of ''One, Two, Buckle My Shoe'' and Louise Bourget of ''DeathOnTheNile'' found this out the hard way.

** Other would-be blackmailer victims include Miss Blanche from ''Cat Among the Pigeons'' and Leopold from ''Hallowe'en Party''. Other characters who "knew too much" include Donald Ross from ''Lord Edgware Dies'' and Mrs Upward from ''Mrs [=McGinty's=] Dead'' -- as well as the principal murder victims in ''Three Act Tragedy'', ''TheMurderOfRogerAckroyd'', ''Cards on the Table'', ''Evil Under the Sun'', and ''A Caribbean Mystery''.

** An example that's neither a blackmailer nor the principle murder victim is Salome Otterbourne in ''DeathOnTheNile'', who witnesses the murder of Louise Bourget (see above), goes to tell Poirot, and gets to invoke HisNameIs before being shot dead by the killer.

** In Part 3, [[spoiler:Enya]] is killed by Dio and Steely Dan (Dio supplied the weapon) [[spoiler:so she can't reveal how [[TimeStandsStill The World works]]]]. The kicker: [[spoiler:Even while dying, it was clear that Enya would ''never'' have thought to betray Dio like that]]. [[SmugSnake Steely Dan just laughs about that.]]

* In ''GhostTrick'', this was the reason that [[spoiler:Sith arranged for the deaths of Jowd, Cabanela, the Professor, and Lynne.]] All of them [[spoiler:had some interaction with/knowledge of the Temsik meteor, and he wanted to be the only one to know about its existence]]. Because those were the same people that [[spoiler:Yomiel, the owner of the last shard of the meteor, wanted dead]], this worked out fine... [[spoiler:until Yomiel realized that he himself fell under this trope, and Sith was [[OhCrap preparing accordingly]].]]
* This happens a ''lot'' in the ''AceAttorney'' series.

* In ''PsychoPass'', [[spoiler:Kagari]] is killed when they find out [[TheAwfulTruth the true form of the Sibyl system]].

** ''NorthByNorthwest''

* This is essentially the reason that ''TheBoys'' haven't been brutally butchered by ruthless "[[BewareTheSuperman superheroes]]" the Seven; the only reason they aren't dead is that they have even more damaging information on someone that The Seven fear more.

* ''OnePiece'':

* ''SnakesOnAPlane'': The catalytic event for the eponymous serpents upon the aircraft.
* Subverted slightly in ''AdventuresInBabysitting'' -- one of the kids had taken a {{Playboy}} magazine that could get the crime boss put away, and the presumption the criminals made, of course, was that the kids had read it, plus the fact that they'd met at all meant they knew too much. The magazine was returned, and the crime boss' underling resigned, knocking him out along the way.

* In ''AmericanBeauty'', [[spoiler:Col. Fitts kills Lester to make sure he doesn't tell anyone that he's gay.]]

* Victor from ''BurnNotice''. It ends sadly...

''The'' most common motive for bad guys to go after innocent people and [[TruthInTelevision the reason that the FBI has the Witness Protection Program]].

* In ''Series/{{The X-Files}}'', Mulder knows entirely too much right from the start, and then gathers more information along the way. When attempts to get him to come to the dark side fail, the Syndicate try to destroy him instead. Since Mulder is more valuable to them alive than dead, they tend to do terrible things to people he cares about. Arguably the worst was giving Scully an inoperable tumor that spelled a slow and painful death for a season ([[spoiler:until a cure is found by Mulder's snooping ways, of course]]).

* In ''Videogame/FalloutNewVegas'', if you convince Veronica to leave the [[KnightTemplar Brotherhood of Steel]] for the Followers of the Apocalypse in her personal quest, [[spoiler:several fanatical Paladins will massacre a Followers outpost and then try to go after Veronica since they see her as a heretic (which to be fair, she is) who ''might'' end up spreading knowledge about the Brotherhood that they're devoted to keeping secret. After fighting them off, Veronica is left horrendously traumatized, but she's sure that she made the right choice in leaving the Brotherhood.]]

* In ''Anime/FutureGPXCyberFormula'', Osamu Sugo leaves the Missing Link F-1 team after knowing of his boss Smith's plans to use Asurada, the computer system created by Hayato's father, as a weapon of mass destruction. He soon disguises himself as Knight Schumacher, in order to keep an eye on Hayato, as well as Smith and his men. During his racing duel with his rival Bootsvorz, Smith attacks Osamu from behind with his helicopter's missile for exposing said secret. Osamu gets better, but ends up injuring his eye.

* This is essentially the reason that ''TheBoys'' haven't been brutally butchered by ruthless '[[BewareTheSuperman superheroes]]' the Seven; the only reason they aren't dead is that they have even more damaging information on someone that The Seven fear more.

* In the ''Series/DoctorWho'' serial ''The Gunfighters'', Johnny Ringo is in Tombstone looking for fellow MagnificentBastard Doc Holliday, and the barkeep recognizes him, and [[TooDumbToLive threatens to go to the Earps]].\\
\\
This was the Doctor's justification for kidnapping Barbara and Ian. Couldn't have them revealing the existence of advanced aliens, after all.

** Implied in an episode after a teenage girl breaks into the Warehouse to coerce Artie to help her save her brother (as in, she knows about the Warehouse and now we have to do something about it). They seem like the kind of folks who consider death to be a (albeit viable) last resort, though.

** It's not until quite a bit later in the story that the audience is shown exactly what he had uncovered. At first it seemed that he'd discovered little more than that there ''was'' an AncientConspiracy, and his knowledge shouldn't really have been a threat to them yet. But in fact, he'd also realized that [[spoiler:all of Amestris was a giant transmutation circle]], a fact that was the lynchpin of the entire conspiracy.

* In ''MassEffect1'', on Noveria the volus, Han Olar, asks an asari commando about to kill him if he'll get a [[GenreSavvy "you know too much speech?"]] Fortunately, Shepard saves Olar before the commando can kill him.

* In ''FanFic/WinterWar'', [[spoiler:Hisagi]] kills Iemura for discovering that [[spoiler:he is a FakeDefector]], even though they were (theoretically) on the same side and Iemura was offering his support, because he didn't believe that Iemura could keep the secret. The guilt eventually drives the killer into HeroicBSOD to the point where his [[EmpathicWeapon zanpakutou]] has to take over his body just to keep him alive.

Somebody is involved in something dirty, or just [[KickTheDog did something nasty]]. Could be TheGovernment, could be TheMafia or TheSyndicate, could be GeneralRipper, a CorruptCorporateExecutive or an AncientConspiracy. No matter what bad guy was involved, somebody saw it all, heard it all, or somehow caught wind of what's going down (or what went down), and the bad guy in question has found out about the witness.

** Sent in a message to [[spoiler:Professor Eifman]] just after he figured out the true agenda of [[spoiler: Celestial Being's founder]], and just before [[spoiler:the Thrones attack the base]], killing him in the process. Either sent by [[spoiler:[[BigBad Ribbons Almack]]]] or by [[spoiler:[[MasterComputer Veda itself.]]]]

** In episode 13, [[spoiler:Shirley Fenette]] gets shot to death for knowing that [[spoiler: Rolo Lamperouge isn't Lelouch's brother.]] The fact that [[spoiler:Shirley]] wanted to help [[spoiler:reunite Lelouch with his ''real'' sibling, Nunally, eliciting Rolo's jealousy]] doesn't help, either.

* ''Anime/{{Monster}}'': If someone possesses any evidence that Johan Liebert exists, that's enough to have Johan arrange for them to die. The exceptions to this are his sister (whom he considers his "other self"), General Wolf, and Dr. Tenma (the latter two [[IOweYouMyLife saved his life]]). [[TheCorrupter Though, he's got]] [[BreakTheCutie his own plans for them.]] [[StrikeMeDownWithAllOfYourHatred And they are just as evil.]]
* In the ''VampirePrincessMiyu'' TV series, this partially is what prompts [[spoiler:DarkMagicalGirl Miyu]] to get the [[spoiler: otaku SecretKeeper]] to fall to his death. The fact that [[spoiler:he showed absolutely no understanding about Miyu's nature and what it means to be the Guardian]] really didn't help his case.

** In the Ski Lodge case, [[spoiler:This was the reason for Minako Mochizuki's murder: she found out that two of her three favorite teachers (one of them being the one she ''adored'') were involved in a fraud, so she tried to confront them... and the two strangled her to death and then made it look like she committed suicide. And the third teacher? She killed '''them''' as part of her plot to get revenge for Minako's murder.]]

** In another NonSerialMovie [[spoiler: Touma witnessed a murder commited by his mother's friend, who then kidnapped him and tried to kill him. However, Touma then fell off a cliff and fell in a coma, only waking up ''eight years later''. The killer targets him again, fearing that if he ever recovered his memories, he'd denounce him]].
** Happens to Ran Mouri twice, once in the anime/manga and later in a NonSerialMovie. In the first [[spoiler: she steps inside several room where guys are undressing, but one of them has a secret so he decides to kill her... and he's the killer of the case]]. In the second [[spoiler: she clearly sees the face of a murderer who immediately tries to shoot her dead, and even when she has a huge TraumaInducedAmnesia he still attempts to murder her.]]

** In Part 3, [[spoiler: Enya]] is killed by Dio and Steely Dan (Dio supplied the weapon) [[spoiler: so she can't reveal how [[TimeStandsStill The World works]]]]. The kicker: [[spoiler: Even while dying, it was clear that Enya would ''never'' have thought to betray Dio like that]]. [[SmugSnake Steely Dan just laughs about that.]]
** In Part 6, Whitesnake kills [[spoiler: Jongalli]] as insurance against Jotaro and Jolyne learning who's ''really'' behind the latter's imprisonment--[[spoiler: Enrico Pucci, the prison chaplain]].
* Almost happens twice in ''{{Orphen}}''. First, [[spoiler: [[{{Seers}} Lai]] steps on who everyone believes to be Childman but is actually [[GrandTheftMe Azalie in Childman's body]], and she turns him into a HumanPopsicle.]] Later, [[spoiler: [[BunnyEarsLawyer Hartia]] finds the frozen Lai ''and'' sees Childman!Azalie's shadow in Azalie's form, so she snaps and almost kills him, but he barely manages to escape to Orphen and Co.'s side.]] In the end, [[spoiler: Hartia survives and Lai is de-frozen.]]

* In ''TopTen'' pop star and former science-hero sidekick Glenn Garland is killed because he was going to tell the media about the illegal and repulsive actions of a group which he used to be a part of. The Vigilante from Venus also expressed concern that they were going to try to kill her before she went to trial, for fear that she would incriminate them in her testimony.

* Magnificent Kamen in ''Literature/SailorNothing'' allows no witness to escape to reveal the {{Masquerade}}. The fact that [[spoiler: he's a [[TheHeartless Yamiko]]]] probably has something to do with that.
* In ''FanFic/WinterWar'', [[spoiler: Hisagi]] kills Iemura for discovering that [[spoiler: he is a FakeDefector]], even though they were (theoretically) on the same side and Iemura was offering his support, because he didn't believe that Iemura could keep the secret. The guilt eventually drives the killer into HeroicBSOD to the point where his [[EmpathicWeapon zanpakutou]] has to take over his body just to keep him alive.

* In a movie about the presidential candidate Luis Donaldo Colosio's assasination in Tijuana called ''Colosio: El Asesinato'', the main character is a police officer who works undercover and is asked by the president's former brother-in-law José Francisco Ruiz Massieu to investigate the murder. After a series of investigations, he concludes that the very same party killed Colosio. At the same time, someone is killing everyone involved with the case and murder, including the murderer and anyone who dares to seek the truth. As a result, the main character gets killed in the end as well as his pregnant wife, his partner, the police chief in Tijuana and Ruiz Massieu all because of this trope.

* In ''Film/LethalWeapon'', Riggs is tortured by the bad guys to find out what he knows about their impending shipment, which is [[spoiler: nothing]].

* [[spoiler: Robert]]'s justification for killing Leroy and Destiny in ''MysteryTeam''.

* In ''Film/{{Drive}}'' a gangster uses a crew of low level criminals to rip of a Mafia boss with the intent to later kill them and take the money for himself. When the plan blows up in his face he and his partner decide that everyone involved Knows Too Much and must die so the Mafia never finds out who was really responsible. Ironically, the only survivor of the crew actually does not know anything and was about to leave town.

* Inverted in ''Film/DiamondsAreForever'' concerning the diamond smuggling ring. When one of your own passes you fake diamonds, he knows too much about the circumstances to die. This is demonstrated when Shady Tree rescues James Bond (who had assumed the identity of Peter Franks, a fellow diamond smuggler who Bond had killed) from a retort to question him about where he hid the real diamonds only for Bond to use leverage against him to the tune of $50,000 ("You bring me the real money, and I'll bring you the real diamonds."), and then {{Zig Zagged| Trope}} when Albert R. Saxby reminds Wint and Kidd that they "didn't get the real diamonds. So we need Tree, alive." Wint and Kidd remark on how "that's most annoying" because they had already cut Tree down, as revealed when Bond shows up in his dressing room.

* An interesting variant in ''Literature/{{Animorphs}}'' - the ''heroes'' consider this during the David Trilogy, when the eponymous character turns against them. It makes them pretty uncomfortable, though in the end, they decide on an [[FateWorseThanDeath even more extreme solution]].

** Joyce Reynolds, the 13-year-old schoolgirl from "Hallowe'en Party" (1969). She tries to use her knowledge of a murder to her benefit. Instead, the murderers have her killed, drowned in an apple-bobbing tub. [[spoiler: And what makes this worse is that it's not even ''her'' knowledge, really; she's overheard the child who really ''does'' know about the murder talk about it and has tried to pass it off as her own knowledge for attention.]]
** Another would-be blackmailer victims include Miss Blanche from ''Cat Among the Pigeons'' and Leopold from ''Hallowe'en Party''. Other characters who "knew too much" include Donald Ross from ''Lord Edgware Dies'' and Mrs Upward from ''Mrs [=McGinty's=] Dead'' - as well as the principal murder victims in ''Three Act Tragedy'', ''TheMurderOfRogerAckroyd'', ''Cards on the Table'', ''Evil Under the Sun'' and ''A Caribbean Mystery''.

* ''Literature/HonorHarrington'': Defied in ''Crown of Slaves''. Some Solarians suggest offing [[spoiler: Thandi Palane]], but are warned away by the fact that she is connected to knowledgeable and hardened killers (read: [[MemeticBadass Victor]] [[GodModeSue Cachat]], [[GeniusBruiser Anton Zilwicki]] and [[YourTerroristsAreOurFreedomFighters Jeremy X]]) who would take bloody vengeance, compounding the fact that the person who knows too much is the one they would go to for assassinations in the first place.
* ''Literature/TwentyThousandLeaguesUnderTheSea'': This is the reason why Aronnax, Conseil and Ned Land will remain prisoners of the Nautilus and cannot come back to Civilization. Ever. (Captain Nemo lets them abandon the Nautilus and explore land, but is always in uncivilized shores). Captain Nemo explains:
-->''"... You came to surprise a secret which no man in the world must penetrate—the secret of my whole existence. And you think that I am going to send you back to that world which must know me no more? Never! In retaining you, it is not you whom I guard—it is myself."''

** Bran sees [[{{Twincest}} Jaime and Cersei]] having sex and is then pushed out of a tower for it. During the ensuing coma, he's attacked by an assassin. We later learn that [[spoiler:the assassination attempt is a subversion - he was attacked because [[InsaneTrollLogic Joffrey wanted his father's approval.]]]]
** [[PosthumousCharacter Jon Arryn]] learned about Jaime and Cersei as well, and promptly died under suspicious circumstances. [[spoiler:Interestingly, this is ''also'' a subversion - he was killed because [[MagnificentBastard Petyr]] felt like sowing some discord.]]
** Petyr also has a habit of doing this, murdering [[spoiler: Ser Dontos, whom he used as a catspaw in order to smuggle Sansa Stark out of Kings Landing, and his accomplice in Jon Arryn's murder, Lysa Tully.]]

* Literature/TheEmperorsSoul, Shai is GenreSavvy enough to know she's going to be killed after [[YouHaveOutlivedYourUsefulness she is no longer useful to her captors]] in part because she could blackmail them with the fact that the Emperor was almost killed and they resorted to forbidden magic to fix and conceal this. She doesn't actually want to blackmail them, but they won't believe that.

** Implied in an episode of after a teenage girl breaks into the Warehouse to coerce Artie to help her save her brother (as in, she knows about the Warehouse and now we have to do something about it). They seem like the kind of folks who consider death to be a (albeit viable) last resort, though.

* In ''Series/{{Battlestar Galactica|Reimagined}}'', this is basically why [[spoiler:Tory kills Cally,]] who has learned that [[spoiler: Tory, Cally's own husband Galen, and Colonel Tigh are actually Cyclons]]. Important to note that [[spoiler:Galen]] is ''not'' in on this, and [[spoiler: kills Tory for it]] when he finds out.

* In ''Series/{{The X-Files}}'', Mulder knows entirely too much right from the start, and then gathers more information along the way. When attempts to get him to come to the dark side fail, the Syndicate try to destroy him instead. Since Mulder is more valuable to them alive than dead, they tend to do terrible things to people he cares about. Arguably the worst was giving Scully an inoperable tumor that spelled a slow and painful death for a season ([[spoiler:until a cure is found by Mulder's snooping ways, of course.]]).