Summary
It's the next day, and the streets have erupted into chaos. A newspaperman calls "extra, extra!" and is surrounded by a dense crowd eager to read all about it. We see that the newspaper has printed a letter that the murderer himself has written. The letter taunts the police for ignoring the letter he initially sent to them, goading the public to stop him in time to prevent him from taking another victim.
Street justice starts to take shape. Antsy people picturing themselves as good Samaritans are quick to incite a mob against any man they find suspicious talking to a child. A crowd gangs up on an older man in glasses, who, however ill-advisedly, was simply making polite conversation with a young child.
Meanwhile, officials are stumped. We're shown a group of aristocratic gentlemen in fine suits smoking with complex cigar holders talking about how confounded they are by the murder.
The police have resorted to pseudo-science to develop a psychological profile of the killer, analyzing his fingerprints and the handwriting from his letter to make assumptions about who he might be and, therefore, what sort of asylum to find him in. The police search the crime scenes, the forest, and the asylum for any lead whatsoever. They come up woefully short. It's clear that government officials are running out of ideas, which means dissatisfaction in the streets will only mount further.
Things hit a boiling point when the police begin to shake down the underworld. After sweeping the streets looking for the killer, the police descend upon a speakeasy and systematically interrogate every person in the place. Unsurprisingly, the criminals in the speakeasy openly loath the police. The majority of them are detained after these interrogations, often on charges unrelated to the murders. One man, for example, is arrested as a suspect in robbing a fur shop.
Then a group of powerful gang members meet to discuss the increased amount of heat the police are putting on the underworld. Here we meet two prominent characters, Der Schränker (who will emerge as the leader of the underworld) and Franz (a lovable, if hapless, burglar). They discuss the fact that this hunt for the killer is cutting into profits from criminal enterprises.
Simultaneously, we watch a meeting of top law enforcement officials, lead by Inspector Karl Lohmann. They look just like that group of aristocrats sitting around the table, and talk about how all of their leads are drying up. Lohmann, finally, suggests that they sweep the residencies of all former asylum inmates who had a history of violence against children, looking for materials that may have been used to write the letters.
Schränker, during his meeting, suggests something more radical. He decides that it has now become the underworld's responsibility to catch the child murderer; otherwise, the police will never effectively end their investigation—and, therefore, the gang's profits will dry up. He declares that every street person in the city will be mobilized as a member of a sprawling surveillance unit. Every corner in the city will be watched by these people and, since their presence is so routine, no one will be suspicious of these street people for simply being on the street.
Analysis
Even though M came out two years before Hitler and the Nazi party came to power in Germany, Lang still had a keen sense of how the concoction of a weak government and extreme public unrest could prove explosive. Much of this segment of the film is dedicated to showing us exactly the excesses of the angry mob, instilling a crucial moral ambiguity. What is in fact more terrifying, a child murderer on the prowl or a scared, blood-thirsty populace? We don't know what motivations drive this crowd. Is it justice, revenge, or something else altogether?
Throughout this section of the film, we see government officials portrayed as ineffective aristocrats. Infamously, this is the reputation of the Weimar government. After Germany was defeated in World War I, Germany was wracked with a humiliating debt as part of the the armistice ending the war. The Weimar government was viewed as incapable of truly standing up for the German people in the face of the wars victors, and the government's reputation only worsened as rapid inflation took hold of the country.
Hence, the contrasts Lang draws between the government officials and the people on the street is poignant, as it articulates that these are really two different worlds within Germany with two totally different concerns. Lang shows us exactly how the government is failing the people, yet that doesn't mean he draws a sympathetic picture of the masses. They are, after all, out for blood.
These juxtapositions are somewhat akin to the Soviet filmic tradition of dialectical montage as theorized by Sergei Eisenstein. The idea with dialectical montage is that a filmmaker can juxtapose two images through editing and inspire ideas in the viewer that could not be communicated through narrative. Hence, when we see the ineffective police juxtaposed with the mad crowd, we come to understand how they are in tension—and how neither is particularly sympathetic.
Interestingly, all of the sympathetic characters in this part of the story are criminals. When the police raid the speakeasy, we don't exactly have any animus to the criminals in the bar. Here is a group of people living their lives, having a good time, and suddenly they are getting harassed.
Dialectical montage is also used to develop this sympathy. When Lang cuts between the meeting of the gang members and the meeting of the police officials, we see the former actually putting together a plan to catch the killer and the latter spinning their wheels.
Equally interesting is the juxtaposition of Schränker and Inspector Lohmann. Lang, again, doesn't try to develop the pathos of either of them, but we do start to develop a more nuanced understanding of this society we're viewing where an underworld boss has more influence than a police official. Later in the film, Lang will unpack exactly why this is so troublesome.
