Chalk M
After following Hans Beckert and a potential victim around the dark alleys of the city, the blind vendor's friend draws an M on his palm with chalk and slaps Beckert's back. Beckert, thus, has been marked "M" for murderer. This M is not just the most iconic image from the film, but the literal icon of the film. Beckert finally sticks out of crowd as the murderer for the first time in the film.
After all, nothing has differentiated Beckert prior to this. He dresses the exact same way as every other man on the street, and for that matter his thirst for blood is matched by the teeming masses waiting to exact revenge on any poor soul who gets mistaken as the criminal. But with the M, Beckert finally stands out. In fact, only with the M does he stand out. Lang once remarked that every person has a little M in his palm—as cryptic and illuminating a statement as the film itself.
Window Display
Just before Beckert pursues his new victim, Lang treats us to the most dazzling image in the movie: the shop window full of shining metal objects. This is a peculiar display, with surgical implements, a sculpture made from spoons, and a mirror frame with metal objects that might be knives or scalpels. Lang uses it to entrance the viewer much like Beckert himself becomes entranced when he sees a young girl in the reflection of this mirror. Through this shop window, we enter the psychological space of this killer and thus better understand the psychosis that takes Beckert over, and that he will later profess in the courtroom scene. This is German Expressionism par excellence.
Balloon
Twice in the film, Beckert buys his potential victims this unsettling balloon that grotesquely resembles a child. It is a large, pill-shaped object with a face drawn on and paper legs and arms dangling from its sides. It looks so helpless, floating in the air and dragged along. The child-like balloon is dragged by a string, and so too are these innocent children who think nothing of the man buying them trinkets and fruit, leading them down shadowy streets.
Print on Screen
Fritz Lang puts a lot of text on the screen throughout the film, including a bulletin on a lamp post, newspapers, and Beckert's letter to the newspaper. Every time we see print, it's talking about the murderer himself or the murders of children in grizzly detail. Perhaps there is some conclusion to be drawn here about Lang's feelings about the media, but it's notable that all of this text appears on screen in Lang's first sound film. Silent films, of course, often featured title cards explaining scenarios and displaying dialog we can't hear, and Lang has not quite let go of the trope in M. Just like how title cards in silent film tell us about things we can not hear, the text in M tells us about violence we never observe.
Shadows
Presaging the film noir craze in Hollywood during the '40s and '50s, Fritz Lang makes prolific use of shadows for dramatic effect in M. There is a constant play of shadows either announcing a character's arrival or creeping into another character's space. So much of this film is about the tension between the shadowy underworld, the masses on the street, and government authority. It's significant that shadows tend to creep into so many frames of this film, and considering the gang's brutal efficacy, Lang builds a savvy allegory of the dark forces gaining momentum in the late Weimar era.
