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The Unsolved Mystery

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"The unanswered mystery is what stays with us the longest, and it's what we'll remember in the end."

In Mystery Fiction, the most common ending is the one where the mystery is solved. The detective figures out who the murderer is, the mask is pulled away, the villain shouts "And I would have gotten away with it too if it wasn't for You Meddling Kids," loose ends are tied up, and everyone (except the villain, of course) goes home happy.

Not so with some cases. In some cases, there are no answers. In some cases, the detective doesn't even know the right questions. This isn't just a Karma Houdini, where the bad guy gets away without consequences. This is where the characters - and the audience - don't even know who the bad guy is or where to start looking or perhaps what the hell just happened.

Stock Unsolved Mysteries are those from history that have inspired many stories. It is a common feature of a Mockstery Tale, when the mystery plot is just pretext for philosophy or psychological drama. See also Criminal Mind Games, Riddle for the Ages, and What Happened to the Mouse? Compare That One Case. For a whole setting comprised of those, see World of Mysteries. Can very often result in an Audience-Alienating Ending.


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    Comic Books 
  • During the time between DC Comics' events Zero Hour: Crisis in Time! and Infinite Crisis, the mystery of who killed Thomas and Martha Wayne, the parents of Batman, had actually been this, part of a number of sweeping changes editor Dennis O'Neil wanted for the masked vigilante.
  • The main storyline of Web of Spider-Man #113-116 (June-September, 1994) is famous for introducing a murder mystery and never resolving it. The story arc has photographer Lance Bannon, a long-serving supporting character, working to develop a picture in the darkroom of the Daily Bugle. It contains the only glimpse of the unmasked face of Armored Villain FACADE. Bannon is murdered within said darkroom, and the investigation casts suspicion on several major and minor characters who have access to the offices of the Bugle, including J. Jonah Jameson himself. "Who is FACADE", and "Who killed Lance Bannon"? The storyline ended with no definite answers and the initial plan may have been to continue the tale in subsequent issues. But issue #117 introduced The Clone Saga and all other ongoing storylines were dropped. FACADE has since made a couple of cameos (in 2009 and 2012) whose main point was to remind readers that the case is still open.
  • Marvel Team-Up #65-66 (January-February, 1977) had another Chris Claremont sub-plot with no proper resolution, this one involving a murder mystery. A "mystery woman" is seen keeping surveillance over two high-ranking members of the Maggia, Marvel's stand-in of The Mafia. Later, we learn that the woman acted as a "lone wolf" vigilante and (as said in the issue) "did a Punisher-type number" on the entire governing body of the criminal organization. While several of the mysteries Claremont introduced in his issues of this title received resolutions, the identity of the female vigilante was never resolved.

    Films — Live-Action 
  • Absence of Malice: The disappearance and probable murder of union official Joey Diaz acts as a Plot-Triggering Death, but his fate is never revealed. Michael Gallagher, who is falsely implicated in Diaz's death, chooses to force the authorities to make a statement clearing him rather than try to solve the case. Gallagher's mobster uncle does seem riled up by the investigation, but his involvement isn't confirmed.
  • Aguirre, the Wrath of God: It's never revealed what Don Pedro de Urzúa was holding in his hand, IF he was holding ANYTHING.
  • The Bank Job: It's never conclusively revealed which of the many parties involved in the eponymous robbery is guilty of of murdering Major Singer and Bambas, or whether their killers are working together or not. In-Universe, the epilogue mentions their murders are never solved.
  • The Pledge: The case is never solved and there are no details on the murderer except that he's a tall man and he died in a car crash approximately 15 minutes before the hero could learn his identity and catch him. Tough luck.
  • Memories of Murder, based on the Real Life Hwaseong serial murders of Korea.
  • In Minority Report, John Anderton never finds out what happened to his missing son. At most, Samantha implies he died shortly afterward.
  • This is the main drive of the plot of Mr. Holmes, an adaptation of the novel A Slight Trick of the Mind (see below).
  • Black Death is about a group of soldiers who are sent out in order to investigate an idyllic village that seems to have been spared from the pestilence. Pretty much everything that they see in the village, whether it be a resurrected girl, a woman with supernatural powers, or the lack of disease, could have a rational explanation, or could in fact be the work of demonic powers. No one ever finds out.
  • The homicide case in Zodiac remains unsolved. The protagonist is pretty convinced that one suspect in particular is the Zodiac Killer, but his theory is never proven conclusively. This is Truth in Television.
  • In The White Ribbon we never learn who committed the crimes.
  • The Thing (1982). One of the main mysteries of the film is who, exactly, sabotaged the blood samples kept in storage. Early on, they narrow it down to either Gerry or Dr. Copper, neither of whom turn out to be The Thing. The other mystery is whether or not Childs became a Thing when he went missing shortly before the confrontation with Blair. The film ends with MacReady and Childs resigning to death from the arctic cold, both of them unsure if the other is human.
    • For what it's worth, comic book continuations of the movie have it that MacReady is unambiguously human and that Childs was infected at some point.
  • Bullitt. The Cowboy Cop kills a key witness whom he was supposed to bring in alive, so they never find out who is behind the organized crime operation. Movie over.
  • In The Hunter, Martin hears about Doomed Predecessor Jarrah's work several times and eventually finds his skeleton, which has a bullet hole through its skull, but it’s never revealed who killed Jarrah. It could have been the company he quit working for, hunters from a rival company after the last Tasmanian tiger, the loggers whose jobs Jarrah was threatening with his environmental activism, or a random hunter who shot him by accident while hunting non-endangered animals.
  • In Picnic at Hanging Rock, we never learn how or why the girls vanished. The novel did have a chapter that explained it, but the publishers decided to keep it a mystery in most editions.
  • Who sent the tapes and drawings to the family in Caché?
  • Broken Flowers does not reveal who sent Don the plot-instigating letter about his son, or if he really does have a son in the first place.
  • After Midnight: By the end of the film it is established to everyone's satisfaction that the thing which is attacking Hank's house is not a figment of his imagination, and is also not a mundane animal like a bear or a puma. We don't find out what it is, and we also don't find out why it appeared after his girlfriend left him.
  • Who Killed Captain Alex? Not even the director knew. The answer ended up being the intro to an entirely different movie.

  • Sherlock Holmes:
    • The story "The Five Orange Pips", from The Adventures of Sherlock Holmes. Though Holmes is certain that the murderers, high-level members of The Klan, are on a specific ship, said ship apparently sinks at sea, and their identities are never determined.
    • The Problem of Thor Bridge states that there were problems even Sherlock Holmes couldn't solve, but they were not published by Doctor Watson because the audience would have felt cheated:
      Some, and not the least interesting, were complete failures, and as such will hardly bear narrating, since no final explanation is forthcoming. A problem without a solution may interest the student, but can hardly fail to annoy the casual reader. Among these unfinished tales is that of Mr. James Phillimore, who, stepping back into his own house to get his umbrella, was never more seen in this world. No less remarkable is that of the cutter Alicia, which sailed one spring morning into a small patch of mist from where she never again emerged, nor was anything further ever heard of herself and her crew. A third case worthy of note is that of Isadora Persano, the well-known journalist and duellist, who was found stark staring mad with a match box in front of him which contained a remarkable worm said to be unknown to science.
  • Mitch Cullin's A Slight Trick of the Mind features an elderly Holmes dealing with three cases, two in the past and one in the present. Holmes solves two of them, but the third, the disappearance of Mr. Umezaki's father, completely stymies him: he cannot remember meeting Mr. Umezaki's father, despite evidence that he has done so, and has burned the volume of Watson's journal that probably would have allowed him to reconstruct the man's fate.
  • In The Sherlockian, an obsessed Holmes fanatic kills himself after realizing that the lost Conan Doyle diary he's been seeking for most of his life had been destroyed. Unable to live with the prospect of never knowing what Doyle had written in it, he stages his suicide to look like murder for his fellow Sherlockians' benefit. Played with and double subverted when the Holmes fan who successfully investigates his death discovers the diary does still exist, but contains an admission that would seriously tarnish Doyle's (and therefore Holmes's) image. His companion destroys the diary, leaving Doyle's secret forever The Unsolved Mystery for the rest of fandom.
  • In the 1632-universe short story "The Vice President's Plane is Down", someone sabotages the eponymous plane, although everyone onboard survives except for a Disposable Pilot. The authorities initially investigate the crime as an attempted political assassination, but other potential motives show up. Another passenger on the plane was an aristocrat about to disinherit his brothers, who may have decided to kill him first. Additionally, it is suspected that the dead pilot was involved in a counterfeiting ring and alarmed his co-conspirators with his Suspicious Spending. The only witness to the crime flees town before he can be questioned. The story ends with the police chief admitting that he has no idea who the sabotage was really intended to kill, no way to pursue further leads, and no suspects for two out of the three possible motives.
    • The Grantville Gazette short story "A Change of Hart" has the Hart brothers and their supervisor discovering someone at the explosives factory has been tampering with the production line scale to get away with stealing two pounds of explosives from every package they send out. They fix the scale and implement better security, but have no way of identifying or punishing the thief or thieves. The incident mainly serves as a Friendship Moment to make the three characters put aside their long-standing differences.
  • Bret King Mysteries: In The Comanche Caves, the gang's new friend Ned expresses hope that he'll find the lost loot from a long-ago train robbery. An outlaw jumped onto the train and stole a gold shipment at gunpoint. He threw the gold off the train as it passed a canyon, only to fall to his death in the process. The gold has never been found, and some people think that the robber had an accomplice waiting to pick it up, or that treasure hunters found it years ago. The gold is a Red Herring and the gang never learns what happened to it.
  • Frederick Forsythe's book The Day of the Jackal. The titular assassin is killed trying to carry out his plot against Charles de Gaulle, but his real identity remains unknown to the end.
  • The Colorado Kid by Stephen King. Two reporters tell their intern about the mystery of the Colorado Kid: a guy found dead on the island, even his name unknown until a year later. Not only is who or what killed him unknown, but nobody knows why he was on the island (he didn't live there) in the first place.
  • The Cat Who... Series:
    • In book #27 (The Cat Who Went Bananas), not only do the characters not find out what happened or who was responsible for the deaths of the book's victims (the actor who died in a car accident after supposedly being on drugs, and Alden Wade's wife who was shot by a sniper), the readers don't, either! It's also never quite confirmed if Alden was responsible for the theft of the book that was stolen from the new bookshop and subsequently turned up among his belongings.
    • During the events of book #28 (The Cat Who Dropped a Bombshell), Qwill attends a family reunion for the Ogilvie-Fugtree family, with plans to write a column on the subject, but it's called off when two rabbit hunters go into the woods and only one returns. The other is confirmed dead, but his murder is never solved for lack of evidence.
    • All three major mysteries in book #29 (The Cat Who Had 60 Whiskers) fall under this.
      • The cause of the two major fires in the book — the Old Hulk (which was being renovated into a senior center) and Qwill's barn — is never discovered.
      • The thieves who stole Nathan Ledfield's treasures from the museum that was to house them are never caught.
      • Libby Simms, who dies of a bee sting, is confirmed to have died of foul play when it's found someone stole her kit to counteract bee venom — but just who did so is never identified.
  • Played with in Rainbows End: the main villain is revealed to the reader in the beginning of the book, but none of the characters figure out who it is. The trickster, on the other hand, might or might not be an A.I. and is only ever seen as a holographic rabbit — not even his name is known.
  • John Grisham's The Associate. In the end, Kyle McAvoy never learns who Bennie Wright really was, who he was working for or why he wanted the Trylon-Bartin documents. Kyle even points out that he couldn't have been Bennie's only spy at Scully & Pershing; Bennie had knowledge he could only have gotten from an inside contact, a partner no less.
  • This happens unintentionally in Raymond Chandler's The Big Sleep. One of the murders is never explained, and when it was pointed out to Chandler, he found himself surprised to realize that even he didn't know who had killed that victim. Although there is an accumulation of evidence pointing to a particular solution for that case, it just lacks a concrete "yes, that's definitely the solution" moment to confirm it.
  • The Nancy Drew story The Clue in the Old Album is kick-started when Nancy witnesses a man steal an old woman's purse during a concert. Nancy goes after him and manages to retrieve the stolen property, learning on its return that the woman didn't care about anything in her purse except several letters. From there the story veers off on a completely unrelated tangent, and though the woman remains a central character, no one ever learns what was in the letters, or why they were so important.
  • The Crying of Lot 49 combines this with Interrupted by the End, coming to a close seconds before the mystery may be brought closer to solution. Why? Because Thomas Pynchon enjoys messing with you. The novel is sometimes said to be the first of its own kind — "anti-detective fiction", where only the search itself and the questions asked matter, not the answers.
  • The titular teen from The Body of Christopher Creed is never found, neither as a runaway nor as a corpse (a body is found, but the deceased is unrelated to the case). At the end, the protagonist receives several letters from people claiming to be Creed, one of which he decides to consider as genuine.
  • Murder in the Mews: Downplayed in "Dead Man's Mirror." The murder is solved, but it's never revealed who Gervase suspected of defrauding him when he summoned Poirot to his mansion, or if his suspicions were accurate. Poirot does note that the secretary and estate manager are both likely suspects, but never pursues this further.
  • Somebody Owes Me Money: Even after the killer is exposed it's still unknown who took Chet's money from the apartment.
  • Teen Power Inc.:
    • Late in The Sorcerer's Apprentice, a thief at the elementary school steals money from Liz and Tom's younger brothers. The person Tom and his brother suspect of the thefts is seemingly exonerated (and helps catch a mugger who has been terrorizing the adults of the town), and Tom admits that he never did learn who the elementary school thief is.
    • In Breaking Point, one of the past mysteries about the potential Haunted House is revealed (along with the present day ones), but there is still nothing to explain other parts of the Back Story. Specifically, it remains unclear why the builder of the house disappeared while leaving his money behind, the next owner claimed the house was haunted, or seven subsequent tenants unexpectedly died of an apparent illness at the same time.
  • 2666: Much like in real life, the serial murder investigation is never concluded.

    Live-Action TV 
  • The show Unsolved Mysteries, of course.
  • The Law & Order franchise has done this a few times, usually in the form of cutting to the credits right before the verdict in a controversial trial is read, or ending without revealing the outcome of a tough decision that the main character(s) or guest star is forced to make. Which is a Truth in Television on its own level: despite what shows like Perry Mason can lead you to think, a trial rarely can solve the mystery - most of the time, it can only establish what a reasonable person, relying on the evidence collected much earlier, should think about the claims put forward by prosecution and defense.
  • Done in the Cracker episode "One Day A Lemming Will Fly." A teacher, in custody as a suspect, confesses to the murder of a school pupil, but then when he is alone with Fitz, tells him that he didn't commit the murder — but feels so guilty about his treatment of the boy (not to mention all the pressure the public, the police and especially Fitz put him under to "confess", lasting nearly two whole episodes) that he said he did it anyway. The real murderer is never identified, nor are any plausible suspects ever put forward. Worse, Fitz wasted so much time on this teacher, and the case has acquired such a high-profile, that his boss decides to ignore his pleas that he got it wrong and still try and convict the man for the crime.
  • The Adena Watson case on Homicide: Life on the Street. In fact, a lot of cases end up not being solved, since Homicide stuck very close to real life.
  • One Seinfeld episode had Jerry getting increasingly frustrated that his Girlfriend of the Week refused to taste a piece of apple pie and wouldn't tell him why. Despite many efforts, he never learns why she turned down the pie, declaring the mystery "one for the ages."
    • Similarly, in "The Seven," Jerry's Girlfriend of the Week wears the same dress on all of their dates with George, and Jerry tries to figure out why. This eventually drives him crazy and she dumps him before he can find out when she catches him starting to go through her clothes.
      Jerry: What in God's name is going on here? Is she wearing the same thing over and over again? Or does she have a closet full of these, like Superman? I've got to unlock this mystery!
  • In the How I Met Your Mother episode aptly titled "The Pineapple Incident," Ted never does find out how or why a pineapple ended up on his nightstand. Eight years later, he finally finds out where it came from. The Captain likes to leave one on his porch as a symbol of hospitality. Drunk Ted stole it years before he ever met the Captain and it had absolutely no connection to anything else in that episode.
  • Farscape: who killed Salis in "Durka Returns"? Especially since one of the two main suspects is a regular character, and there's a common Epileptic Trees fanon that it was actually another of the regulars.
  • Doctor Who: What the hell was the Midnight Creature?
  • So many things about Twin Peaks. Namely, is MIKE a good guy or a bad guy? What about The Man From Another Place? What was the deal with The Log Lady? Who was that kid with the creamed corn? How is Annie?
    • In fact, David Lynch initially intended the central mystery of the series — that of Laura's murder — to remain unsolved as well, but Executive Meddling forced him to change this.
    • The movie, Twin Peaks: Fire Walk with Me, opens up even more questions. Why was David Bowie distorting the space-time continuum? What happened to the Chris Isaak character? Who was the Jurgen Prochnow character from Laura's dream? What was that monkey about, and who is this Judy person it mentions?
  • The Prisoner (1967). Why did Number Six resign? We never know. Whose side was the Village on? We can only guess. Was Number One a clone? A twin? A hallucination?
  • The "Ass Crack Bandit" from the Community episode "Basic Intergluteal Numismatics". The two main suspects are disproven and another attack occurs. Jeff and Annie try chasing the bandit, but give up when Shirley tells them that Pierce has died. At episode's end, the ACB remains at large. A writer retweeted a part of the script for The Grand Finale that implied that Annie was probably the ACB, but this could've been a joke.
  • House: Why was Kutner Driven to Suicide? Which was the point, according to Word of God.
  • One CSI episode has a series of knife attacks, followed by murders of the same victim, committed by a man wearing a full-body latex suit. His pseudonym is Ian Moone, but that quickly proves an anagram of "I am no one". It later turns out all his targets were people who were publicly upstanding citizens with dark secrets, making the killings a form of Vigilante Execution. But despite all they learn about him, they never find out Moone's true identity and they never catch him.
  • Northern Exposure: In "All is Vanity", a man who no one in the small town knows drops dead of natural causes in Joel's waiting room, and the episode ends with it remaining unknown who he was or what he was doing in either Cicely or the waiting room.
  • Probe's "Computer Logic": Austin is working on solving the murder of Donald Stonheim, a pilot who died while circumnavigating the Hudson Bay in 1921 and recently recovered. The police believe it to be an accident, but Austin noticed something in the left posterior fontanelle which indicates that Donald died before the crash. He plans to solve this mystery purely from the inside of his workshop, discovering motive, method, murder with the power of observation.

  • Ruby Quest. A girl wakes up in a coffin in some mysterious place, frees this guy from his prison downstairs, and together they start to make their escape and try to find some answers, in that order. They do get away in the end, and many answers were found, but so very much was left to shadows as well. Justified, though, due to the nature of the game. Word of God is that, had the players done a couple of things differently, more answers would have been uncovered. Notably, Filbert was supposed to explain a lot, but he ended up kind of, well, dead.

    Video Games 
  • Two in Daughter for Dessert:
    • Why exactly did Saul give the protagonist free legal representation?
    • Who stole the toaster? Mortelli apparently knows, but refuses to say.
  • This is what happens if you don't get the Good Ending in Persona 4. The Bad one acts as the sad outcome, and the characters never ask themselves about the contradictions.
  • It's easy to go through the Laura Bow adventure games and have no idea what is going on. Even if you manage to get the good ending, it's possible you haven't figured out quite everything behind the mystery.
  • An in-universe example. In Batman: Arkham City, there is a sidequest named "Watcher in the Wings", about a mysterious stalker that Batman keeps seeing.When you finally confront him, he names himself Azrael and talks in riddles about a prophecy involving Batman and Gotham City. Batman simply says "I don't believe in fairy tales" and Azrael leaves. Hardcore Batman fans may recognize the character, but neither Batman nor the audience has any idea what he's predicting. Azrael would later return to confront Batman once more in Batman: Arkham Knight.
  • In Cyberpunk 2077, V learns that the new mayor of Night City, Jefferson Peralez, and his wife Elizabeth have become the center of a Government Conspiracy in which someone killed the previous mayor and has been brainwashing the Peralezes for unknown reasons, giving them Fake Memories and altering their personalities with the player being unable to discover the truth behind it all. Johnny Silverhand theorizes that rogue AIs could be responsible, however the Mysterious Stranger from the "Sun" ending Mr. Blue Eyes can be spotted spying on them, and the Ambiguously Evil infrastructure company Night Corp has performed similar experiments in the past with Peralez having been one of their beneficiaries. What makes it even more bizarre is that it appears to be a case of Brainwashing for the Greater Good, as their captors seem interested in turning them into the "perfect" political couple and if Locked Out of the Loop Mr. Peralez declares his intent to combat homelessness.
  • The subplot regarding Matt's father in Another Code R is dropped about two chapters before the end of the game and not brought up again, even after most of the plot points are solved. Supposedly, the plan was for him to have a Spin-Off game in which the story would have been resolved, but the company went bankrupt before anything could be put into place.
  • In Back to the Future: The Game, Doc kicks off the plot by using time travel to solve an unsolved mystery: who was the arsonist who destroyed a speakeasy in 1931? Not only did he not find out (a flying brick stunned him when he tried to investigate), but he was himself blamed. A few episodes later, Marty learns that it was Edna Strickland... and alters history so that everyone else knows it too, meaning that the Doc of the altered timeline never had any reason to go near the speakeasy in the first place.
  • In-universe in the Ace Attorney games — any incident that ends without a conviction gets a code of two letters and a number (e.g. DL-6) and becomes a cold case until a conviction is made or the Statute of Limitations expires. The case going unsolved/the criminal never being convicted is also the usual Bad Ending in situations where the player can get a Game Over.

    Web Comics 

    Web Original 
  • Several episodes of Bedtime Stories (YouTube Channel) cover several of these cases, including mysterious disappearances reported in American and Canadian national parks, as well as how the Dyatlov Pass hikers all died.
  • BuzzFeed Unsolved investigates both the existence of the supernatural and real-life crime mysteries, though Foregone Conclusion dictates that the cases covered by them are left open-ended. Ryan's search for proof that ghouls and demons exist also has yet to be confirmed, though the evidence that he does manage to accumulate could point either way.

    Real Life 
  • Truth in Television, unfortunately:
    • The Alphabet murders of Rochester, New York. From 1971 to 1973, three girls aged 10 to 11 were murdered in the vicinity of the city. The case got its name because it was noticed that each victim had an Alliterative Name: C.C., M.M., W.W. A theory that they were connected to the similar Alphabet murders of California (1977-1978, 1993-1994), which were eventually resolved, is considered doubtful because the captured serial killer targeted adult women.
    • The Atlanta Ripper. An unidentified serial killer active in Atlanta and its vicinity. He/she killed more than 20 black women and dark-skinned "mulatto" (mixed race) women from 1911 to 1914 or 1915 (which was the last "canonical" murder is in dispute). Most of them had their throats slit, but levels of additional mutilations on the bodies varied widely. The police and/or the press suspected the involvement of the Ripper on a few murder cases dating from 1917 to 1924, though the similarities were questionable. There are multiple theories on the identity of the killer, including one that claims that there was never a singular killer and that the original murder(s) and the publicized details inspired a large number of copycat killers. There simply are no definitive answers in this case.
    • The Axeman of New Orleans. An unnamed serial killer, active from 1918 to 1919. He/she broke into the residences of his/her victims at night, took hold of various blades in the household (mostly razors or axes), and proceeded to attack the sleeping victims in their beds. Six victims were either killed instantly or died later as a result of their wounds, six were injured but managed to survive. The surviving victims were uncertain what happened to them and could provide no definite description. A letter attributed to the killer claimed: "They have never caught me and they never will." Which remains true.
    • Bible John. A serial killer with only three confirmed victims, active from 1968 to 1969. All women, aged 25 to 32, whom he met at the Barrowland Ballroom, a dance hall in Glasgow. He met the women, escorted them home, and then raped and strangled them. The sister of one of the victims, who briefly shared a taxi ride with him and her sister, recalled him introducing himself as "John" and making various religious references in his part of the conversation. The only other clue in this case is that the killer kept the women's handbags, possibly as a trophy. The case was never solved, and the only witness died of old age in 2010. While still considered a cold case, chances of it ever receiving a resolution are considered slim.
    • The Black Dahlia. In January, 1947, the mutilated remains of Elizabeth Short, waitress, were located in Los Angeles. The murder received its nickname as a film reference, and attracted much attention. Despite decades-long investigations, the murder was never solved and several of the key suspects have long passed away.
    • The Hwaseong serial murders, a series of 10 rapes and murders of women in the provincial South Korean city of Hwaseong, taking place from 1986 to 1991, were this for many years. The killer did not seem to have a preference for a particular age group, as the youngest victim was 14 and the eldest 71. About 21,280 suspects were interrogated in one of the most extensive police investigations in history. The killer was not apprehended until 2019, when a DNA match confirmed that convicted murderer Lee Choon-jae was responsible for the killings.
    • Jack the Ripper, although there have been many suspects and even some (suspect) DNA evidence.
    • The Zodiac Killer. A killer mostly targeting couples, with a habit of then sending taunting letters to the press and including mysterious cryptograms. Five victims were killed and two injured, in confirmed cases from 1968 to 1969. The killer is considered a suspect in additional cases dating from 1963 to 1970, and in a letter he/she claimed to have killed 37 victims. The case was never solved.
    • For 44 years the California serial home invader/rapist/killer known as the Golden State Killer/Visalia Ransacker/East Area Rapist/Original Night Stalker, went unsolved. Until April 25th 2018. Where it was revealed that we he was former cop, Joseph Deangelo, 33 years after his last known rape and murder
  • The Cleveland torso murders, a series of shockingly brutal killings in Depression-era Cleveland, Ohio. Most of the details remain a mystery, including who the victims actually were. The killer targeted vagrants and sex workers, so only two (Edward Andrassy and Florence Polillo) out of at least a dozen were ever identified. The "at least" is because the exact number of victims, and even the exact timeline, is still unclear. What is known is that the police could not possibly have fucked up harder. Eliot Ness (yes, that Eliot Ness) became involved and employed methods like torturing a suspect (Francis E. Sweeney, who, coincidentally, was the cousin of one of Ness's political rivals) and burning a shantytown to the ground. The police also murdered another suspect, Frank Dolezal, after beating a false confession out of him. To this day, there are no leads, although some people believe Sweeney was the murderer based on Ness's largely unfounded suspicions. Oh, and the killer may also have been responsible for the lesser-known "murder swamp killings", which took place a train ride away in New Castle, Pennsylvania. The only thing positive about the killer is that it was a physically strong man with at least some knowledge of anatomy.
  • The second colony of Roanoke Island. Established in 1587, one of the governors decided to return to England to gather supplies, since lack of supplies was why the first colony failed. War with Spain prevented him from returning for three years. When he finally did return, the colonists had all disappeared, with only the word "CROATOAN" carved on a fencepost as a clue to their fate. To this day, no one is sure what became of the colonists.
    • Of course, there's the small matter of the native Croatoan tribe who lived on the other side of the bay, who, when they were finally investigated, turned out to have a surprising number of members with blond hair and white skin. Rendering this more of a Real Life Subverted Trope.
      • Or at least, that is one of the prevailing theories of what happened to them. Without DNA testing, there's really no way to know for sure, so it ends up being more a case of "Probably Solved Mystery But Without Proof We'll Never Know".
      • A similar case is the disappearance of Amelia Earhart. Several artifacts believed to come from her plane (and a possible skeleton, although the bones themselves are lost and there's considerable evidence both for and against) have been found on Gardner Island, close to her last planned refueling stop, but whether the plane landed there or the items washed onto shore after a crash at sea is unknown.
  • The disappearance of Lord Lucannote . All that was known is that, in the midst of a bitter custody battle with his former wife, she was attacked (pointing the finger at Lucan) and the nanny was found beaten to death. Hours into the investigation, he had his mother pick up the children and visited a friend's house. His car showed up, abandoned and filled with blood (as well as a lead pipe, which was probably the murder weapon), in a town near the coast and Lucan was never seen again.
  • The famous duel between Alexander Hamilton and Aaron Burr has two questions behind it that will never be answered.
    • The first is what caused Burr to challenge Hamilton to the duel in the first place. The only thing we actually do know is that what truly tipped Burr over the edge was a letter from Charles Cooper saying that Hamilton had expressed "a still more despicable opinion" of Burr in private. In their correspondence, Hamilton refused to specify what Cooper might have been referring to and Cooper never publicly revealed it, so whatever the insult was that made Burr finally decide to challenge him will never be known.
    • The second is what actually happened during the duel itself. All we do know is that Hamilton had a hair trigger installed on his weapon yet chose to deactivate it, both men fired their guns, and it ended with Burr killing Hamilton. Hamilton's second stated that he purposely fired into the air, while Burr's second claims that he actually tried to hit Burr and missed. Burr never publicly clarified which one was accurate. The men also could not agree on which man fired first. Overall, pretty much nothing about the duel itself is known nor will ever be known.