A villain held prisoner by the heroes continues to undermine their objectives through their toxic influence.

They have a tendency to spark disagreements between allies (up to and including the spread of a HatePlague), [[HannibalLecture use their captivity to shake the good guys' confidence in themselves]] or to make them feel uneasy by virtue of being closer around than they were as a free agent. Despite the heroes' best efforts, it's usually difficult to keep the villain in the dark about everything that's going on or prevent them from divining weak spots, so the longer they're held the more of a danger they pose, especially should they escape -- meaning it's all but inevitable that they will.

Particularly dangerous cases may pose the threat of a hero's untimely [[TheCorrupter corruption]], if they start listening to the villain's cynical-but-persuasive advice, buying into their [[UtopiaJustifiesTheMeans justifications]] [[IDidWhatIHadToDo for]] [[WellIntentionedExtremist evil deeds]], or being tempted by offers made in exchange for freedom.

Another common scenario is that the villain is held ''secretly'', meaning that if word were to leak out, the captors run the risk of getting in serious trouble with their superiors, being deposed by their inferiors, or losing PR with the general populace.

All in all, it's a good reason to ignore ThouShaltNotKill, but the typical reason for keeping him around is that the villain has some kind of information the heroes need desperately enough for it to be worth the risk. In some cases, murder would be counterproductive or even impossible, if the captive is immortal.

May be a result of ISurrenderSuckers. Compare PityTheKidnapper, a comedic version (which usually involves villains as captors rather than heroes), MightAsWellNotBeInPrisonAtAll, and SealedEvilInACan. Compare and Contrast DefiantCaptive, who is more likely to be a heroic character refusing to submit to their captor. The inverted version often falls under TalkingYourWayOut.
----
!!Examples:

[[foldercontrol]]

[[folder: Anime and Manga ]]

* ''Manga/FullmetalAlchemist'' has Envy, when he was trapped in a flask. He was able to play on May Chang's fear for her clan and talk her into going back instead of taking him to Xing, which allowed him to escape [[spoiler: and obtain a second Philosopher's Stone.]]
** [[spoiler:Homunculus]] did much the same while trapped in his flask, using his knowledge of alchemy and the desperation of his captor to [[spoiler:convince the Emperor of Xerxes to prepare the alchemic circle that destroyed the nation and gave Homunculus a body]].
* ''Manga/SoulEater'''s [[FilleFatale Medusa]], for the brief time she ''was'' imprisoned, did absolutely nothing for [[TheWoobie Crona]] or Maka's peace of mind.

[[/folder]]

[[folder: Comic Books ]]

* The Thing Behind the Wall in ''JohnnyTheHomicidalManiac''. Nny has to keep it trapped by keeping the wall covered in fresh blood, which naturally does wonders for his already fragile sanity. Then the Thing gives two Styrofoam dolls in Nny's apartment sentience; ThePlan was that they'd persuade him to commit suicide and thus release it.
* In ''DarkEmpire'', Luke Skywalker tries a version of this on the Reborn Emperor. He does ''some'' good, [[spoiler: but is ultimately corrupted and his sister needed to talk him around.]]
[[/folder]]

[[folder: Film ]]

* John Harrison [[spoiler: (Khan)]] from ''{{Star Trek Into Darkness}}''. After being locked in the ''Enterprise's'' brig, he almost immediately starts working on Kirk, needling him psychologically, feeding him information as it suited [[PapaWolf his]] [[RoaringRampageofRevenge purposes]], and eventually ending up in an {{Enemy Mine}} situation with the ''Enterprise'' crew, rather than just remaining a prisoner.
* In ''Film/{{U571}}'', the German submarine prisoner continuously causes problems for the American crew, until he is killed.
* In the aptly-named movie ''SuicideKings'', a bunch of amateurs kidnap retired mafia boss ChristopherWalken for somewhat convoluted reasons. Needless to say, Walken turns them all against each other in record time.
* ''TeachingMrsTingle'' essentially uses this as a plot framework.
* In ''Film/TheDarkKnight'' the imprisoned Joker blows up the jail and works on a cop's psyche until he breaks out.
* ''RuthlessPeople'' at first, till it turns into AMatchMadeInStockholm.
* In the film ''Southern Comfort'', the National Guardsmen capture a one-armed French-only speaking local Cajun hunter and trapper, one of the Cajun's who were threatening them. They attempt to talk to him but he only speaks French. Nevertheless, just his presence is enough to poison the group.
* In ''Film/TheAvengers'' movie, [[spoiler: Loki]] is captured early on. Despite the team's best preventive efforts, it ends spectacularly poorly.
** It was so bad that in the end, everyone agrees that the best decision is [[TheSpeechless to put a gag]] [[BoringButPractical on him]] and [[YouCanKeepHer send him back]] to [[spoiler:Asgard]].
* In ''Film/SilenceOfTheLambs'', Hannibal Lecter is a death row prisoner who manages to drive at least one other inmate to suicide, and whose understanding of the serial killer mind threatens to unhinge Clarice Starling.
* Following the vogue of recent movies, Silva in ''Film/{{Skyfall}}'' gets captured as part of his plan to get revenge on M.

[[/folder]]

[[folder: Literature ]]

* In ''Literature/TheWheelOfTime'', the heroes captured no fewer than three Forsaken individually, and between them they covered just about all of the risks inherent to this trope. Asmodean was (sort of) on Rand's side, so the danger he posed was mostly just if word got out about who he really was, but you have to question the wisdom of keeping around a character like [[TortureTechnician Semirhage]], who was once captured by the forces of Light during the War of Power. By speech alone she terrified her guards so badly that they smuggled her out of captivity rather than face the tortures she threatened them with.
* ''Literature/TheSilmarillion''. Morgoth turns the Noldor against each other in Valinor once he was released from captivity. Later, Sauron ended up corrupting and destroying the Númenóreans after they captured him.
* In ''Literature/TheThreeMusketeers'' FemmeFatal Milady de Winter pulls this by seducing her jailer when captured in England, twisting the guy so much that he becomes an assassin, attacking The Duke of Buckingham (also a HistoricalInJoke, as this event really happened).
* In the ''SecondApocalypse'' series, Anasûrimbor Moënghus during the time he was a prisoner of Cnaiür urs Skiötha's tribe. He seduced Cnaiür's mother, convinced Cnaiür to kill his father, and talked Cnaiür into setting him free.

[[/folder]]

[[folder: Live Action TV ]]

* ''Series/BuffyTheVampireSlayer'': In season four, Spike was often this to the Scoobies.
* Ben from ''Series/{{Lost}}'' makes his first appearance as the captive "Henry Gale", and spends his entire time in captivity playing mind games with the survivors and attempting to turn them against one another.
* A Silurian warrior woman in series 5 of ''Series/DoctorWho'' . She managed to convince one of the people guarding her to act on her worst impulses.

[[/folder]]

[[folder: Video Games ]]

* In ''VideoGame/MetalGearSolidPeaceWalker'' the player can capture Zadornov and keep him in a cell in an attempt to convince him to join your cause. Ultimately, he breaks out numerous times and goes into hiding, forcing Big Boss to waste time locating and recapturing him each time. [[spoiler: Each time he escapes, he's been released by Paz, who's using him to divert attention while she makes modifications to Metal Gear ZEKE.]]
* In ''VideoGame/CallOfDutyBlackOps2'', Menendez (the game's big bad) gives up quite easily when the player catches up to him about 2/3rds of the way through the game. He's taken back to the ''USS Obama'' to be interrogated. You find out why he gave up so easily during the interrogation scene when [[spoiler:the power goes out as a result of Menendez's followers launching an attack. Menendez mysteriously gets the drop on your buddy and then escapes; you find out later that your buddy is ''working'' with Menendez and in fact leads him to the ship's central computer where Menendez uploads a virus he had smuggled in.]] Whoops. Also, if you're dumb enough to [[spoiler:spare him at the end of the game, and you didn't sacrifice Harper earlier, then he breaks out ''again'' and kills Woods]].
* This is why the Brotherhood is trying to control The Darkness instead of destroying it in ''VideoGame/TheDarkness 2''. [[spoiler: The Brotherhood captured The Darkness and guarded it for decades. And it kept talking to them until they eventually decided that destroying the world was the only way to save it.]]
* At the end of ''{{VideoGame/Diablo}}'', the titular BigBad is imprisoned in a crystal which is fused with the hero's body and mind, as Diablo simply cannot be killed. Cue the second game, where the hero is [[spoiler:completely overtaken by Diablo who wears his body like a cloak. While this counts as Main/DemonicPossession, it is implied that the process was gradual and did not rely solely on magic, but also at least partially on the personal influence and inherent malice of the demon.]] The same story also happened in the past with [[spoiler:Tal Rasha and Baal]].

[[/folder]]

[[folder: Webcomics ]]

* Cyndi from ''Webcomic/PennyAndAggie'' [[spoiler:manipulated her captor into attempting suicide.]]
* This was [[BigBad Faden's]] entire schtick in ''{{Exiern}}''. He was captured a couple of strips in, spent almost the entire time in captivity and still proved to be an effective villain.

[[/folder]]

[[folder: Western Animation ]]

* SelfDemonstrating/TheJoker on the ''WesternAnimation/BatmanTheAnimatedSeries'' episode "MadLove", who was able to talk his psychiatrist Harlene Quinzel into becoming HarleyQuinn while still in Arkham. It was implied early in the episode that he compromised the ones before her in a similar fashion.
* Batman does this in ''WesternAnimation/JusticeLeague'', when captured by Lex Luthor's villainous team. [[spoiler: He bribes Ultra Humanite to save the Justice League from Luthor's EvilPlan and take down the team from the inside, frames the perfectly innocent Cheetah as his accomplice, drives a wedge between team members and generally makes a nuisance of himself, all while restrained. Then, as the kicker, he reveals in the climax that he could have escaped at any time but stuck around 'to keep an eye on' the Injustice Gang.]]
----