This is a common plot device often used to kickstart a story, or get it into high gear.

Basically, the heroes discover that some bad guy is up to no good. The problem is that for whatever reason. the hero has trouble getting people to believe him. Maybe because [[JustAKid the hero is a kid]], because the bad guys are [[VillainWithGoodPublicity respected authority figures]], or because [[CassandraTruth their scheme sounds]] [[RefugeInAudacity outlandish]]. They may have tried to deliver a warning ''without'' getting evidence first and been [[YouHaveToBelieveMe dismissed out of hand]]. Or maybe [[ReasonableAuthorityFigure the authorities]] do believe them, but can't act without evidence. Either way, the heroes need proof of what the bad guys are doing in order to get anyone to believe them, and the ensuing adventure becomes essentially about that. Of course, this plot isn't ''quite'' able to [[ScienceMarchesOn catch up in this day]] and age of hand-held phone recorders/cameras/camcorders in cell phones; because that would get in the way of the ''drama'' of trying to acquire evidence. Often they'll come up with [[ReinventingTheTelephone different ways of recording information]] that's complicated enough for the plot.

This is also a way to get otherwise reluctant heroes involved in the plot. If for no other reason than the fact that since they can't convince anyone else, it's all up to them to solve the problem.

This can also affect the genre, and is the catalyst of many a AmateurSleuth and SnoopingLittleKid story.
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!!Examples

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[[folder: Anime ]]

* The main obstacle for L of ''Manga/DeathNote'' is not in deducing [[SerialKiller Kira]]'s identity, but in finding proof beyond a shadow of a doubt to ''support'' his deduction.
** Not unreasonable, given that Kira is using a magic killer notebook to commit his crimes. Without proof, who would believe that?
* What Tenma of ''{{Anime/Monster}}'' occasionally tries to do about Johann. The rest of the time he's attempting to kill him.

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[[folder: Film ]]

* Many 1950s horror films used this plot device, specifically applied to teenagers (i.e. those who paid to see drive-in movies) who found out some horror or other, but the adults wouldn't believe them.

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[[folder: Literature ]]

* ''{{My Teacher Is an Alien}}'' starts off with Susan Simmons finding out that, well, [[ExactlyWhatItSaysOnTheTin look at the title]]. She knows full well no-one will believe her, and her efforts to try to get evidence are what set the story in motion.
* ''Literature/ASpyInTheNeighborhood'' is about three boys who think a certain neighbor may be a spy. They want to get the cops on her case, but in order to do that, they need to find proof of some sort, so they basically spy on her.
* ''Literature/JenniferTheJerkIsMissing'' starts out this way, as Malcolm needs her babysitter, Amy, to believe that he did indeed witness a kidnapping. They then try to prove it to the adults, which doesn't work.
* ''Literature/{{Animorphs}}'' starts off with the kids trying to expose the Yeerks' silent invasion to the world, in hopes that once the world knows what's going on, they'll be able to fight back. This plan becomes less significant as the series progresses, in favor of simple guerrilla war, but ultimately succeeds near the end.
* This happens in a few of the AlvinFernald books by Clifford B. Hicks
* A major plot thread in ''Literature/HarryPotterAndTheHalfBloodPrince'' involves the titular character being certain that GoldfishPoopGang leader Draco Malfoy is up to something, and trying (without success) to prove it. Of course, this is in large part due to the fact that the primary responsible authority figures [[spoiler:(Dumbledore and Snape) already know he's up to something and want Harry to have as little to do with it as possible.]]

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[[folder: Live Action TV ]]

* In ''Series/BabylonFive'', several episodes involved a search for evidence to prove that [[spoiler: President Santiago's death was an assassination engineered by his successor, not an accident]].
* ''Series/TheFugitive'' combines this with SternChase, as a wrongfully-accused man flees from the law as he tries to find the evidence to prove who the real killer was.
* ''Series/TheXFiles''. If Scully had a catch phrase, "We need scientific proof!" would be it.
* ''Series/EerieIndiana''
* On ''Series/SavingGrace'', Rhetta is a forensic investigator and does all kinds of tests on any items that Earl gives Grace to prove his angelic existence. Boy, does she find proof.
* Subverted in ''Series/StarTrekDeepSpaceNine''. When Sisko sets out to find proof that the Dominion is going to attack the Romulans, resident spy-in-exile Garak tells him the best way to find it will be to manufacture it themselves.
* Happens a lot in ''Series/WhiteCollar''. The criminals are often known right away; the trick is gathering enough evidence to allow the FBI to do anything about it.
* A common occurance on ''Series/{{CSI}}'' and its spinoffs. Often occurs on cases where the evidence isn't yielding as many leads as the [=CSIs=] need to make the case.
* About halfway through every episode of ''{{Monk}}'', the titular detective will figure out who did it. Without exception, the person he accuses will have an airtight alibi (once, the guy was ''in space'' at the time of the murder), and Monk will have to find the one thing that doesn't fit.

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[[folder: Tabletop Games ]]

* ''Hunter: The Vigil'''s Network Zero has proof of nearly goddamn anything. The problem is getting people to take it seriously.
** Not helping is that the same high-tech world they're relying on to break the news has some strict limits. Posting footage of a werewolf mauling someone on YouTube breaks its content guidelines.

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[[folder: Video Games ]]

* The early plot of ''VideoGame/MassEffect1'' revolves around the protagonist uncovering evidence to prove that the villain is actually the villain to the not-so-omniscient council of very visible politicians.
* Your first mission in ''PhantasyStar 2'' is to recover a recorder from the Bio Systems laboratory in order to find out why the lab started making monsters. This is but the first step in proving that the [[InstantAIJustAddWater Mother Brain]] is not as benevolent as she appears to be...
* In ''BaldursGate II'' you're required to find overwhelming evidence of the younger Roenall's wrongdoings, as all complaints about him have to go through...him. So you need something very convincing to convince his superior to break protocol and get rid of him.
* In the NES ''ComicStrip/DickTracy'' game, as Dick is a by-the-book cop, you have to follow the trail and find a LOT of evidence before you can arrest any of the big villains, even though you can confront them directly at any time. Arresting them prematurely earns you a stern talking to from your boss. (Much to the chagrin of WebVideo/TheAngryVideoGameNerd.)
* ''KingdomHearts'': In Wonderland, Sora and company must clear Alice's name regarding an assassination attempt at the Queen and find evidence against the Heartless.
* In ''VideoGame/BeyondGoodAndEvil'', this is basically the entire plot: to prove the [[ArmiesAreEvil Alpha Sections]] are secretly associated with the [[PlanetLooters Domz]] they're supposed to protect against.
* In VideoGame/{{Fallout|1}}, after saving the mayor of a little town from an assassination attempt, he asks you to gather evidence on the person (a local crime boss casino owner) he knows is behind it. You can either side with the crime boss, pretend to be an assassin available for work to make him do an EngineeredPublicConfession thanks to a tape recorder the mayor gave you, or just plain bugging his room.

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[[folder: Web Original ]]

* In ''DeptHeavenApocrypha'', the main characters involved in Nessiah's plot spent months trying to convince Asgard that [[spoiler:Hector had raped him]]. To make things worse, it looks like said character's [[VillainWithGoodPublicity influence]] is going to quash all possibility of a fair and just trial.

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[[folder: Western Animation ]]

* Zim of ''InvaderZim'' is a DevilInPlainSight whose PaperThinDisguise shouldn't ''need'' any proof to expose, but the earth is largely populated by idiots so [[HeroAntagonist Dib]] is continually after "proof" (generally, a shot of Zim not in disguise) -- he's managed to get it on more than one occasion, but since FailureIsTheOnlyOption he always loses it even if he otherwise thwarts Zim's latest {{Zany|Scheme}}[=-=]but-EvilScheme.
* A common occurence for Candace in ''PhineasAndFerb'', despite the guys not being evil (at least not to us). Their inventions are always in plain sight, but their sister goes through gread ordeals to actually get their mom to see it, resulting in this trope several times by using cameras et.c.
* In the series ''WesternAnimation/DragonsRidersOfBerk'', a series continuation of the movie ''WesternAnimation/HowToTrainYourDragon'', TheHero Hiccup knows the old man named Mildew not only destroyed the village's supply of weapons to defend the village and framed the dragons, he even saw the framing objects in Mildew's hut. But after Mildew destroys the evidence, Stoic tells Hiccup that while he believes his son, he cannot punish Mildew for treason without hard evidence.
* The Deputy Dawg cartoon "Diamonds In The Rough" has the deputy tasked with finding a diamond smuggler, but the sheriff tells him not to make an arrest without evidence. A haphazard golfer swings by, and Deputy Dawg deduces that the golfer is the smuggler and the diamonds are in the golf balls. After he accidentally swallows some golf balls, Deputy Dawg is at the doctor with the golfer, and the X-ray shows the diamond-laden golf balls in DD's stomach.
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