History Main / DetectiveMole

* In ''Next Time I'll Aim for the Heart'', the protagonist is a French serial killer named Franck Neuhart, who is also one of the gendarmes investigating this very murder spree. The story is based on the real story of a gendarme named Alain Lamare (cf. RealLife).

'''''Note:''''' This is a SpoileredRotten trope, that means that '''EVERY SINGLE EXAMPLE''' on this list is a spoiler by default and most of them will be unmarked. [[Administrivia/YouHaveBeenWarned This is your last warning]], only proceed if you really believe you can handle this list.

* Inverted in one ''ComicBook/GreenManor'' story, where the detective looking for the elusive SerialKiller John Smith (who has baffled police and profilers alike, because he never seems to have the same MO or psychological profile, other than leaving "I will kill again" at the scene) realizes [[spoiler:there is no serial killer: every crime was committed independently and [[JackTheRipoff signed John Smith]]. So as to bring an end to this universal alibi,]] the detective exposes himself as the killer.

* In ''VideoGame/PhoenixWrightAceAttorneyTheContemptOfCourt'', [[BigBad Lyle Hemlock]], the leader of the Aculeus organization, disguises himself as a detective character named [[spoiler:Robert Snow]] to investigate and manipulate various people related to his organization like puppets to [[ControlFreak ensure that things always go his way]] and ultimately escape with a rare metal called enigmium, worth several million dollars in cash.

[[folder:Films]]

* In ''Film/AceVenturaPetDetective'', a murder and two kidnappings (one dolphin and one Dolphin) were investigated[[spoiler:, and also instigated, ]]by police chief Lois Einhorn.

* ''Film/{{Horns}}'' movie adaptation features a variant of this. Ig Parrish is accused of the rape and murder of his girlfriend, which had been committed by [[spoiler: Lee, who is Ig's best friend and lawyer. Lee actually tries to frame Terry (Ig's elder brother) as the culprit.]]

* In ''Film/SummerOf84'', a group of teenagers believe the [[SerialKiller Cape May Slayer]] to be one of the police officers working on the case. [[spoiler:They're right, and the officer uses his position to arrest someone else for his crimes when the kids get too close to the truth.]]

* In ''Film/ISeeYou'' the disappearance of a boy is thought to be a copycat of crimes committed years before, for which a man was imprisoned. [[spoiler:It turns out that the detective investigating the case (the main character) is responsible for all of them.]]

** In ''Literature/HerculePoirot's Christmas'' the murderer turns out to be [[spoiler:Superintendent Sugden, the local police officer involved in investigating the murder]].
** In ''Literature/TheMurderOfRogerAckroyd'', [[spoiler:the new Watson figure, who replaces Hastings as Poirot's sidekick and the novel's narrator, is the killer]].
** In ''Literature/ThreeActTragedy'', the culprit is one of the {{Amateur Sleuth}}s whom Poirot and Mr. Satterwhaite collaborated with.
** In ''Literature/{{Curtain}}'' the murderer is [[spoiler:Poirot himself. Well, he's *one* of the murderers, anyway--still not the main one.]]
* In Gaston Leroux's novel ''The Mystery of the Yellow Room'', the murderer turns out to be [[spoiler: Frederic Larsan, the Lestrade-like police detective who competes with the AmateurSleuth for solving the crime]].

* In Val Mcdermid's ''The Distant Echo'', four students literally stumble upon the body of a young woman, and are immediately suspected of the crime. The reader is led to wonder if it was one of them who killed her and in that case who. As it turns out, the real killer is [[spoiler:the first police officer on the scene.]]
* The murderer in Creator/IsaacAsimov's ''Literature/TheCavesOfSteel'' is [[spoiler:in charge of the investigation, and specifically picked his old friend, the main character, to handle it]].

* ''Literature/KillingTime:'' The attempts on Tim’s life are all committed by the chief of police conducting the investigation.
* In the ''Literature/LordDarcy'' novel ''Too Many Magicians'', the true identity of the murderer/Polish spy known as 'Goodman Fitzjean' is [[spoiler:Commander Ashley, the Naval Counterintelligence officer assigned to track Fitzjean down]].

** In ''This Night's Foul Work'', [[spoiler: Ariane Lagarde, a highly-respected forensics expert]] deliberately misleads the whole investigation team by setting up a false but very convenient culprit. Adamsberg and Danglard do think that someone connected to the crimes is in their team... [[spoiler: but they spend most of the book suspecting Lieutenant Veyrenc.]]
** In ''The Ghost Riders of Ordebec'', the Ordebec murderer is none other than [[spoiler: Louis-Nicolas Emeri, the ''gendarmerie'' officer initially in charge of the investigation.]]
* In ''Literature/ArseneLupin in Prison'', [[spoiler:the Inspector Ganimard from the first half of the story, hired by Baron Cahorn to stop Lupin's newest scheme, is an impostor employed by Lupin, as opposed to the real Ganimard who visits Lupin in jail in the second half of the story.]]

* In ''Series/TheMrsBradleyMysteries'', the killer in the final episode turns out to be [[spoiler: Inspector Henry Christmas]].
* In season 3 of ''Series/NipTuck'', serial killer The Carver turns out to be [[spoiler: Quentin Costa and Detective Kit [=McGraw=], who's investigating the case, is his sister and accomplice]].

* Happens several times on ''Series/BabylonFive'', due partially to the fact that the eponymous station is where folks go (at least earlier in the show) when they get ReassignedToAntarctica. Many of the security guards work there simply because they had nowhere else to go, and more than a few are easily bribed. The most notable example, however, would be [[spoiler: Garibaldi's assistant Jack]], in the first season.

* On ''Series/{{Justified}}'' US Marshal Raylan Givens tends to run into those types of moles. In season one, Sheriff Hunter Mosley turns out to be working for a Miami drug cartel and is called in to investigate when his relative botches a hit on Raylan. In season 2 it is an OpenSecret that the Benetts are the biggest marijuana growers in the state and Sheriff Doyle Bennett regularly investigates and covers up crimes committed by his brothers. In season 4, the FBI agent in charge of investigating the Tonin crime family has been on their payroll for years. When Raylan goes looking for fugitive Drew Thompson who disappeared in Harlan County 30 years ago, he is helped by new sheriff Shelby Parlow who not only is reluctantly working for crime boss Boyd Crowder but also [[spoiler: is Drew Thompson]].
* In [[spoiler:the second season of]] ''Series/{{Forbrydelsen}}'', [[spoiler:Lund's new sidekick Strange is the killer]].

* While not murder ([[SeriousBusiness it's just treated as it]]) or explicitly stated, the possibility ''is'' raised in ''Recap/CommunityS5E03BasicInterglutealNumismatics'' -- the caught Ass Crack Bandit (who drops quarters down people's ass cracks) turns out to be innocent of that crime, and the ending montage implies it could be one of several recurring characters, some of them having been involved with the investigation. The series finale virtually confirms it, pointing to [[spoiler: Annie.]]
* ''Series/TheDoctorBlakeMysteries'': In "The Visible World", the murderer is [[spoiler:Inspector Llewellyn Sullivan of Special Branch]]. He claims to have come to Ballarat to supervise the investigation because of the political sensitivities surrounding the case. He was actually in town to kill Alderton and Hannam to tie up loose ends.

* A major ongoing plot in the second season of ''Series/NCISNewOrleans'' involves a search for TheMole inside the Department of Homeland Security. TheMole turns out to be [[spoiler:Agent Russo]], the DHS agent placed in charge of the investigation.
* ''Series/{{Vera}}'': In [[spoiler:"Old Wounds"]], Vera investigates a cold case when skeletal remains are found in the woods. The murderer turns out to have been the supervising officer on the original missing person case, who encouraged the investigating officer to do a slipshod job and write the case off as a runaway.
* ''Series/MurderSheWrote'': In [[spoiler:"The Monte Carlo Murders"]], the murderer is revealed to be the police inspector Jessica has been assisting in the investigation.

* ''Series/{{Banshee}}'': In the season two premiere, Lucas gets called in to investigate the robbery of an armored car from the Indian casino. [[spoiler:The same one Lucas, Carrie, Sugar, and Job knocked over earlier in the episode.]]

** Kenton in “Two Bodies in the Lab” is an agent working on a case with Brennan and he tries to kill her when the truth comes out. Booth’s RoaringRampageOfRescue saves her just in time.
** The tech expert in “The Brother in the Basement.” He helps Angela go through a suspect’s computer but is really distracting everyone to try and keep them from realizing he’s the killer.

* [[spoiler:Tohru Adachi]] in ''VideoGame/{{Persona 4}}'' turns out to be responsible for the serial kidnappings, two murders, and seven attempted murders.
* [[spoiler:Goro Akechi]] in ''VideoGame/{{Persona 5}}'' turns out to be responsible for the mental shutdowns and psychotic breakdowns, and is TheDragon to BigBad [[spoiler:Masayoshi Shido]]. Apparently in the ''Franchise/{{Persona}}'' series, you can never trust a detective [[spoiler:whose name is A--chi]].

*** [[spoiler:Manfred von Karma]] ends up prosecuting Miles Edgeworth for the DL-6 Incident. He committed the crime, ''Edgeworth's father's'' murder.
*** [[spoiler:Damon Gant, back when he wasn't the chief of police yet,]] was involved in the SL-9 Incident. He killed Neil Marshall and framed Ema Skye for it.

*** [[spoiler:Luke Atmey]] isn't actually [[spoiler:the thief he was looking for]], but he's the mastermind behind [[spoiler:his heists]].
*** [[spoiler:Furio Tigre]] was Maggey Byrde's defense attorney ''and'' the culprit of the crime she was being tried for. In fact, [[spoiler:he intentionally defended her badly so she would be declared guilty for his crime]].

*** [[spoiler:Tyrell Badd, one leg of the Yatagarasu]], who [[spoiler: made sure to be the detective assigned to the Yatagarasu case specifically to destroy any evidence his partners left behind]]. The other two members are [[spoiler:Byrne Faraday (a prosecutor) and Calisto Yew (a defense attorney)]].
*** [[spoiler:Prosecutor Jacques Portsman]] is a member of the international smuggling ring that Interpol is investigating.
*** [[spoiler:Prosecutor Bansai Ichiyanagi/Blaise Debeste]] killed Jill Crane and pretended to be unrelated to the crime.
** [[spoiler:Daryan Crescend]] from Interpol killed another Interpol agent and came up with an alibi to disconnect himself from the investigation.
** [[spoiler:Detective Bobby Fulbright (or rather, a spy who killed the real Fullbright and took his place)]] investigates the murder of Clay Terran while being the culprit himself. [[spoiler:He also killed Metis Cykes several years earlier, another murder you have to solve.]]
* [[spoiler:Scott Shelby (the Origami Killer)]] from ''VideoGame/HeavyRain'', who is [[spoiler:pretending to be a private eye hired by the victims' families so he can get access to and dispose of any evidence that implicates him.]]
* A sub-plot in the ''Series/{{CSI}}'' game ''Fatal Conspiracy'' involves a drug cartel, being investigated by one FBI Agent Huntby. In the second to last case, it's revealed that [[spoiler:Huntby was working for the cartel]].

** The first case has PlayerCharacter Kaede Akamatsu working with Ultimate Detective Shuichi Saihara to figure out who committed murder. [[spoiler:Kaede is leading Shuichi towards the horrible realization that she was the one who did it in true [[Literature/TheMurderOfRogerAckroyd Roger Ackroyd]] fashion. And then in the final case, it's subverted: Kaede was being [[FrameUp framed]] by the ringleader all along, although even she didn't know.]]
** Chapter 6 reveals through [[spoiler:Shuichi's [[TrumanShowPlot audition tape for the Danganronpa reality TV show]] that he entered the killing game intending to become the first Ultimate Detective blackened, but he never commits any murders in the game.]]
* In ''VideoGame/FalloutNewVegas'', you can assist in an investigation regarding a possible Legion mole within Camp [=McCarran=], the main base of the NCR. You'll eventually learn that the mole is none other than [[spoiler:Captain Ronald Curtis, the very person who assigned you to find the mole and a Legion Frumentarii]].
* Later on in ''Videogame/DiscoElysium'', the {{amnesiac|Hero}} protagonist is presented with the possibility that he might have been a corrupt cop under the mob's payroll who's been using his position to act as a hitman. The question is only answered at the very end by [[spoiler:your original partner, who bluntly states that [[PragmaticVillainy no mob boss would ever use you in that capacity due to your mental instability]]]].
* In ''Videogame/{{Judgment}}'', the killer known as "The Mole" [[note]]called such because he operates at night, not because of the trope[[/note]] that Yagami spends the entire game pursuing is none other than [[spoiler:Detective Mitsuru Kuroiwa, the detective assigned to the case]].

* ''WesternAnimation/DanVs'': In the episode "Dan Vs. Elise's Parents", Dan tries to get Elise's father arrested by manufacturing evidence that he's the head of the mafia. This evidence is enough to convince the police to open their own investigation. The detective they send turns out to be a mole, working for the ''real'' mafia, [[spoiler:whom Elise's ''mother'' is the head of.]]

* Judge Doom is ostensibly the one looking for the one responsible for murdering Marvin Acme in ''Film/WhoFramedRogerRabbit''. He's the one who committed the murder. What's more, he also kills R.K. Maroon before he spills the beans. And was the one behind the company buying Maroon Studios and the Red Car. ''And'' was the one who killed Eddie's brother all those years ago. Moreover, he did all this so that he could destroy Toontown and build a resort area next to the soon-to-be completed freeway. (And, according to one of the first drafts of the script, he was the one who shot WesternAnimation/{{Bambi}}'s mother!) That's one seriously disturbed toon.

* In ''Film/SummerOf84'', a group of teenagers believe the [[SerialKiller Cape May Slayer]] to be one of the police officer working on the case. [[spoiler:They're right, and the officer uses his position to arrest someone else for his crimes when the kids get too close to the truth.]]

* In Val Mcdermid's ''The Distant Echo'', four students literally stumble upon the body of a young woman, and are immediately suspected of the crime. The reader is lead to wonder if it was one of them who killed her, and in that case who. As it turns out, the real killer is [[spoiler:the first police officer on the scene.]]

* In one episode of ''Series/TheCloser'', a [[AssholeVictim man who killed two of his girlfriends]] in the late 90s, but was never convicted because the bodies weren't found, is murdered. The man who lead the first investigation, a Detective Olin who has since retired, is asked to come in and help them with the new murder, because of his insight in the original case and his close relationship with the families of the victims. In the end, it turns out Detective Olin is [[TheLastDance dying]] and, desperate to solve his ThatOneCase, killed the man after torturing him until he revealed where he buried the bodies.

* On ''Series/{{Justified}}'' US Marshal Raylan Givens tends to run into those types of moles. In season one Sheriff Hunter Mosley turns out to be working for a Miami drug cartel and is called in to investigate when his relative botches a hit on Raylan. In season 2 it is an OpenSecret that the Benetts are the biggest marijuana growers in the state and Sheriff Doyle Bennett regularly investigates and covers up crimes committed by his brothers. In season 4, the FBI agent in charge of investigating the Tonin crime family has been on their payroll for years. When Raylan goes looking for fugitive Drew Thompson who disappeared in Harlan County 30 years ago, he is helped by new sheriff Shelby Parlow who not only is reluctantly working for crime boss Boyd Crowder but also [[spoiler: is Drew Thompson]].

* A major ongoing plot in second season of ''Series/NCISNewOrleans'' involves a search for TheMole inside the Department of Homeland Security. TheMole turns out to be [[spoiler:Agent Russo]], the DHS agent placed in charge of the investigation.

* ''Series/JonathanCreek'': Several times. In "Mother Redcap", a police constable is revealed to have killed a judge she was supposed to protect (through a complicated scheme involving electrified alarm clock and stabbing his body afterwards so everyone would think that the stabbing was the cause of death). And in "Coonskin Cap", a detective uses the apparent serial killer in town to kill his colleague and blame the killer.

* FBI agent Robert Hanssen, who sent enormous amounts of intelligence to the Soviet Union and later Russian Federation during a career as a spy that lasted over twenty years, was at one time head of a task force charged with ferreting out the suspected mole in the FBI--himself. The film ''Film/{{Breach}}'' is based on this story
* FBI agent John Connolly was involved in helping mobster James J. "Whitey" Bulger get away with his crimes for as long as he did. Colin Sullivan in ''Film/TheDeparted'' was loosely based on him, while Frank Costello from the same movie is based on Bulger. ''Film/BlackMass'' is a more direct treatment of Connolly and Bulger's partnership. Connolly is currently in a Massachusetts prison for a 40 year sentence after serving a 10 year sentence in Federal prison. It was partially thanks to him that Bulger was able to escape as a fugitive for as long as he did.

* In 1978-1979 in France, a series of various felonies (five asaults, one murder, car thefts...) in the same region was eventually attributed to Alain Lamare, a gendarme who was part of the persons who investigated this crime spree. Lamare was diagnosed schizophrenic and declared non-responsible, so he was never tried.

[[folder:Anime and Manga]]

[[folder:ComicBooks]]

[[folder:Film]]

* In ''Film/SawIV'', Detective Mark Hoffman is revealed to be SerialKiller Jigsaw's second protégé.

* In ''Film/NoWayOut'', the three main characters involved in the investigation of a Pentagon-related murder that is blamed on a [[RedHerringMole supposed Soviet mole]] are each guilty of a crime. One is the actual murderer, another is helping him frame someone else for said murder, and the third is an actual Soviet mole.

[[folder:Fanfic]]

* In ''Videogame/{{Judgment}}'', the killer known as "The Mole" that Yagami spends the entire game pursuing is none other than [[spoiler:Detective Mitsuru Kuroiwa, the detective assigned to the case]].

* The first case of ''VisualNovel/DanganronpaV3KillingHarmony'' has PlayerCharacter Kaede Akamatsu working with Ultimate Detective Shuichi Saihara to figure out who committed murder. [[spoiler:Kaede is leading Shuichi towards the horrible realization that she was the one who did it in true [[Literature/TheMurderOfRogerAckroyd Roger Ackroyd]] fashion. And then in the final case, it's subverted: Kaede was being [[FrameUp framed]] by the ringleader all along.]]

* Taken to the limit in the 1949 noir ''Follow Me Quietly'' in which a serial killer called "The Judge" takes the place of a dummy of himself created by detectives to aid identification so he can listen in on how the investigation is going.

* [[spoiler:Goro Akechi]] in ''VideoGame/{{Persona 5}}'' turns out to be responsible for the mental shutdowns and psychotic breakdowns, and is TheDragon to BigBad [[spoiler:Masayoshi Shido]]. Apparently in the ''[[Franchise/ShinMegamiTenseiPersona Persona]]'' series, you can never trust a detective [[spoiler:whose name is A--chi]].

* Later on in ''Videogame/DiscoElysium'', the protagonist is presented with the possibility that he might have been a corrupt cop under the mob's payroll who's been using his position to act as a hitman. The question is only answered at the very end by [[spoiler:your original partner, who bluntly states that [[PragmaticVillainy no mob boss would ever use you in that capacity due to your instability]]]].

* Judge Doom is ostensibly the one looking for the one responsible for murdering Marvin Acme in ''Film/WhoFramedRogerRabbit''. He's the one who committed the murder. What's more, he also kills R.K. Maroon before he spills the beans. And was the one behind the company buying Maroon Studios and the Red Car. ''And'' was the one who killed Eddie's brother all those years ago. Moreover, he did all this so that he could destroy Toontown and build a resort area next to the soon-to-be completed freeway. (And, according to one of the first drafts of the script, he was the one who shot Disney/{{Bambi}}'s mother!) That's one seriously disturbed toon.

Among the various cops, forensics people, etc., working on a crime scene in fiction, there's a good chance that one person on the team will know a ''lot'' more about what happened than everyone else present ... because they ''committed'' it.