->''"Just you wait, it won't be long.\\
The man in black will soon be here.\\
With his cleaver's blade so true.\\
He'll make mincemeat out of YOU!"''

Creator/FritzLang's 1931 masterpiece about a serial child killer in Weimar Berlin and the people who try to find him: the police, the criminal underworld, and the city's beggars. One of the first examples of FilmNoir, ''M'' provides not only stark black and white images, but also a haunting {{leitmotif}} throughout the film.

Hans Beckert (Creator/PeterLorre) whistles "In the Hall of the Mountain King" by Edvard Grieg from ''Theatre/PeerGynt'', as he buys a balloon from a blind balloon seller for a little girl named Elsie Beckmann. A scene later, Elsie's mother looks for her and can't find her, shouting her name as the camera shows the balloon drifting in the sky.

Police inspector Karl Lohmann, meanwhile, is investigating the serial killings with modern policework, such as fingerprinting and handwriting analysis. The criminal underworld, too, is searching for the killer, since more police on the street is bad business for them and they, too, [[EvenEvilHasStandards are disgusted by the killer targeting children.]]

When Hans whistles "In the Hall of the Mountain King" again in front of the blind balloon seller, the seller tells one of the criminals, who marks Hans with a chalk M on his jacket, so they can follow him. The criminal fraternity goes to more ruthless lengths than the police to catch the killer, and cause a great deal of collateral damage to people and private property, before finally closing in on him. The criminals kidnap Beckert and bring him to a KangarooCourt, where Hans makes an impassioned speech about how he should not be blamed for the murders since he can't help himself, he can't help that he's insane. Despite the nature of the court, the criminal appointed as Beckert's legal representative tries hard to defend him fairly. The 'prosecutor' takes the stance that either for his crimes (if he is not insane) or for his insanity, Beckert has forfeited his right to live and must be exterminated. Beckert desparately tries to he explain that ''he can't help being this way''. The criminals are about to kill Hans when the police bust in and arrest both him and his captors.

As Hans is about to be sentenced by five judges, the mothers outside the courtroom say it won't bring back their children. Elsie's mother says they should have kept better watch. "[[SomeAnvilsNeedToBeDropped We, too, should keep a closer watch on our children]]. ''All of us.''"

!!The film contains examples of:

* AdultFear: Don't leave your kids alone even for a second.
* ArcWords: "Who is the murderer?"
* BadassLongcoat: Der Schränker's leather overcoat. Although see PuttingOnTheReich below; he's not a very likable character.
* BittersweetEnding: Beckert is brought to trial, but the climax establishes that neither execution nor medical treatment seem to be a totally fitting sentence, and it won't bring back the kids anyway. [[{{FridgeLogic}} Although,]] [[{{WorldHalf Full}} by the end of the film a serial murderer/rapist has been brought to justice along with several high ranking mob officials leaving the German public better off for it.]]
* CharacterSignatureSong: Hans Beckert always eerily whistles Edvard Grieg's "In the Hall of the Mountain King" when he goes somewhere.
* ChekhovsGun: [[spoiler:Beckert's compulsive whistling, which leads to his identification as the child murderer.]]
* ChekhovsGunman: [[spoiler:The blind balloon seller.]]
* DramaticDrop: When Franz tells Inspector Lohmann that they broke into the office building to catch the child murderer, the cigar he was smoking falls out of his mouth.
* DreamMelody: "In the Hall of the Mountain King"
* EmpathyDollShot: One of the [[UrExample oldest examples]]: Elsie's ball and balloon in the opening scene.
* EvenEvilHasStandards: A complicated example. Hans disgusts all the criminal bigwigs because he kills children, but they're primarily after him because the police looking for him interfere with their crimes. The "defense attorney" notes the hypocrisy of wanted murderers standing in judgment of another murderer. Hans' final speech also [[MoralMyopia calls them out on their hypocritical "standards"]], pointing out that he does what he does because he is insane and cannot help himself, whereas they simply can't be bothered to learn an honest trade.
* EveryoneCallsHimBarkeep: Der Schränker ("The Safecracker").
* EvilVersusEvil: Most of the conflict happens between the child killer and the organised criminals many of whom were killers themselves (just of adults). Inspector Lohmann and the authorities only played a minor role as a third party.
* ExtraExtraReadAllAboutIt: "Extra! Extra!", shout all the paperboys carrying news of the Beckmann murder.
* ForeignRemake: Joseph Losey's mostly-forgotten 1951 U.S. version transposes the story to post-WWII Los Angeles.
* {{Foreshadowing}}: The game the children play with the ball at the start of the film.
* GermanExpressionism: A late example.
* GollumMadeMeDoIt: Beckert's defense. He's driven by a compulsion that he can't resist.
* GoryDiscretionShot:
** Interesting version; In one scene, the Thieves are torturing a watchman for information in a glass-windowed room, with a crowd of beggars watching from outside. When the leader signals for the torture to start, the beggars move up against the windows so nothing can be seen.
** Also, Elsie's death at the beginning.
* TheGreatDepression: A rare European example.
* GreyAndGrayMorality: Both sides are black with shades of grey. Even a child murderer is not without his sympathetic side.
* HoldingTheFloor: Beckert's long speech at his trial.
* TheHunterBecomesTheHunted: You can pinpoint when Hans Beckert discovers he is being watched and is about to be caught to the moment when he discovers the chalk "M" on his shoulder. Ironically, this is because his intended victim points it out to him.
* IneffectualSympatheticVillain: Hans again. In fact, Peter Lorre was typecast as this role for years afterward. Subverted in that Hans Beckert managed to kill several children and successfully evade the police in the first part of the film and the time before and is only this because of his patheticness and guilt after being caught.
* InsanityDefense: The climax features an analysis of whether it's fair to punish a man for crimes he was compelled by insanity to do.
* IronicNurseryRhyme: The children's singing in the beginning and "In the Hall of the Mountain King" to an extent.
* ItsAllAboutMe: Hans's impassioned speech in his own defense pretty much ignores the pain and suffering he caused and would have continued to cause if allowed to roam free in favor of complaining about how unfair it was for people to blame him for his actions. Especially bad when you realize that even if Hans is mentally ill [[{{FridgeLogic}} he never once sought treatment for his supposedly unwanted impulses]] and instead attempted to remain at large despite knowing what that would result in. Then again seeking treatment for being a pedophile in those days are even worse than today so while being a DirtyCoward it's not like it's an easy choice.
* JerkassHasAPoint:
** Beckert is an insane child murderer, but his condemnation of the hypocrisy of the 'court' standing in judgement of him isn't entirely without merit.
** The prosecutor of the mob trial may be a criminal but he does have a point that whether or not Hans is crazy he is a threat to the children of Germany regardless and killing him would make them more safe.
* JokerJury: The criminals' court at the end (although Hans is far from a hero).
* KangarooCourt: The criminal underworld sets up a court to try Beckert, but it's clear from the beginning that they have no intention to do anything but kill him.
* {{Leitmotif}}: "In the Hall of the Mountain King" used for creepy effect. [[TropeCodifier In fact,]] ''[[TropeCodifier M]]'' [[TropeCodifier practically created the cinematic leitmotif.]]
* MassOhCrap: The furious audience of the KangarooCourt is about to leap on Beckert and tear him to shreds, when they all notice something behind the camera, suddenly freeze -- and begin to put their hands up.
* MatchCut: A crime boss talks to his fellow crime bosses about the problems the child murderer is causing, due to the increased police presence. With a sweep of his arm, he says "I invite--". Cut to another person at a different meeting, sweeping his arm and saying "--your views, gentlemen." The second meeting is a different group of men -- this time detectives -- discussing the same subject. The rest of the scene continues to cut between the different meetings in a similar way.
* MurderersAreRapists: Very, ''very'' subtly implied, and all off-screen. One of the police departments on the child-killer case is a sexual crimes division, and one policeman says to another concerning the child-killer's victims "You know what state we find them in after that." Also, everyone was specifically looking for a male perpetrator.
* NeighborhoodFriendlyGangsters: Deconstructed. The vigilante criminals are only interested in ending the manhunt to restore their criminal endeavors. Hans also points out that their crimes have even less justification than his own.
* NoCelebritiesWereHarmed: Lohmann in his bodily build, mannerisms and modus operandi is very closely modeled on [[https://en.wikipedia.org/wiki/Ernst_Gennat Ernst Gennat]] (1880-1939), the head of Berlin's ''Mordinspektion'' (set up in 1926, the world's first police Homicide division), who introduced many innovations to investigation procedures, e.g. becoming the first man to use the new medium of television to ask the public for information relevant to an ongoing investigation. Gennat among other things headed the investigation of the Grossman and Kürten murders and coined the term "serial killer" with reference to the latter. In his day Gennat was internationally famous[[note]]When Charlie Chaplin visited Berlin, he asked to be introduced to Gennat.[[/note]] and was known to Berliners by affectionate nicknames like "the Buddha of the Alex" (i. e. the police headquarters on Alexanderplatz).
* NoEnding: Probably a LogicalExtreme example. Not only does the movie [[TheUnReveal come to a close right before Hans is given a verdict]], ''there aren't even any credits'', not even a "TheEnd" card like most every film had even in those days. The film cuts to black as the grieving mother whispers "all of us" (see the introduction above), and then it suddenly stops.
* NotSoInnocentWhistle: The killer has a super-creepy whistle.
* OhCrap: The very slow pan around the room after Hans is shoved down the stairs, showing the JokerJury staring at him in unmoving complete silence.
** And, of course, the famous scene where he realizes his coat has been marked and that he's being followed. In fact, this is mostly Beckert's reaction throughout the entire second half of the film.
** See also MassOhCrap above.
* OneLetterTitle: The "M" stands for ''Mörder", aka murderer.
* OrganGrinder: One is among the beggars tasked with keeping their eyes out for the murderer.
* OutOfGenreExperience: For a few minutes, the police procedural part switches into documentary style, complete with voice-over, diagrams, and a giant compass drawing circles on a city map.
* PaedoHunt: The hunt for Hans.
* PoliceProcedural: The police part of the movie is possibly the UrExample of this trope.
* PragmaticVillainy: Part of the reason why the criminals want to stop Hans so much? His presence increases the number of police operating, which in turn interferes with their ability to break the law and get away with it.
* PuttingOnTheReich: What may be seen as a "prophetic" example, since the Nazis weren't in power yet: Der Schränker's long leather coat may be seen as foreshadowing UsefulNotes/TheGestapo; more plausibly his leather-coat and rhetoric have been seen as alluding to Joseph Goebbels, then chief of propaganda of the Nazi party and their ''Gauleiter'' (regional head of the party organisation) in Berlin. Although neither the Gestapo nor Goebbels were known for sporting bowler hats or walking-canes. The Schränker was portrayed by Gustaf Gründgens, who later continued to rise to fame and fortune under the Nazis (partly because Hermann Goering was a fan of his), which became the subject of Klaus Mann's RomanAClef ''Film/{{Mephisto}}''. The story that the film was originally entitled ''Mörder unter uns'' ("Murderer(s) Among Us") and had to be given a different title due to pressure from the Nazis is a legend which Fritz Lang at different times confirmed and denied.
* TheReasonYouSuckSpeech: In his impassioned defense, Hans is quick to note the essential hypocrisy of the court of criminals trying him; he does bad things, but he commits abhorrent acts because he is insane and cannot make himself stop, but they ''choose'' to be criminals when they could instead earn an honest living.
* SerialKiller: Of little girls.
* ShamingTheMob: This is what Hans tries to do. It doesn't work. Except on some audience members.
* ShoutOut: The ''M'' used to mark Beckert inspired the plot of the ComicBook/BlakeAndMortimer album ''Recap/TheYellowM'' and also the 13th ''Franka'' album, ''De dertiende letter'' ("The thirteenth letter") by Henk Kuijpers.
* SilenceIsGolden: Because a silent film was expected to have accompaniment throughout this film is actually quieter than most ''silent films''. The silence of shots like the slow reveal of the mob backed court, and, later, the police coming to stop the mobsters from killing the serial killer makes them so much tenser.
* StabTheSalad: After luring in his next victim, Hans pulls out a switchblade, which he uses to cut an orange.
* SympatheticMurderer: Hans turns out to be one in the end, in spite of his horrific crimes.
* TalentDouble: Peter Lorre couldn't actually whistle, so Lang provided it in a hidden CreatorCameo.
* ThievesGuild: Several of them, it seems, one for each major division of the trade.
* TokenGoodTeammate: To Beckert's surprise, his "defense counsel" at the Criminals' trial actually tries to defend him, and makes a powerful argument at the trial as to why Beckert should be handed over to the police instead of being lynched by the mob.
* TragicVillain: Hans can't help the fact that he's a child murderer.
-->'''Hans:''' But I, I can't help myself! I have no control over this! This evil thing inside me, the fire, the voices, the torment!... It's there all the time, driving me out to wander the streets, following me, silently, but I can feel it there. It's me, pursuing myself. I want to escape, to escape from myself. But it's impossible. I can't escape. I have to obey it. I have to run endless streets. I want to escape, to get away. And I'm pursued by ghosts. Ghosts of mothers. And of those children. They never leave me. They are there, always there. Always, except when I do it. When I... Then I can't remember anything.
* TheUnReveal: Beckert's sentence. The judges are just about to announce it when the film cuts to a mourning mother, who says it doesn't matter, because it won't bring back her child.
* VeryLooselyBasedOnATrueStory: Fritz Lang based the story on several serial killers who had plagued Germany in recent years, including Fritz Haarmann, Karl Grossmann, and Peter Kürten, the "Vampire of Düsseldorf." Haarman and Grossmann are mentioned by name, and Haarmann is the real subject of the children's rhyhme at the beginning. It should be noted that Fritz denied it because it was seen as being tastelessly (for presenting him as sympathetic) RippedFromTheHeadlines.
* VillainProtagonist: Hans Beckert, serial child murderer.
* WeirdTradeUnion: The Beggars' League (taken from Creator/BertoltBrecht's ''Theatre/TheThreepennyOpera'').
* WhatIsEvil: Beckert is pursued by the city's criminal underworld, because the intensive police manhunt is interfering with their business and because they resent police inquiries that imply that they might be associated with a child murderer. When they [[JokerJury conduct a mock trial]] of Beckert, he [[ShamingTheMob attacks]] their sense of [[EvenEvilHasStandards moral superiority]], declaring that he does what he does because he's haunted by unwanted compulsions he can't resist, while they do what they do because they freely chose crime instead of honest work.
* WouldHurtAChild: Hans, a pedophile and murderer of children.
* WritingIndentationClue: The murderer writes a letter to the newspaper, using a single sheet of paper, a red pencil, and a wide windowsill in his apartment as a desk. When the police raid the apartment, they find partial impressions of the letter's words in the sill, as well as bits of red pencil lead. In this case, they already knew what had been written; the indentation and lead bits were, instead, proof that it had been written ''there'' specifically.