They rely on violence and their own deeply flawed instinct (“My eyes can read people”) to identify the culprit, and it all leads them to one person: a local boy with learning difficulties, called Baek Kwang-ho. The actions undertaken at the scene are ruinously sloppy, and their interrogation techniques are even worse.

The police detectives put in charge of dealing with the case (played by Kim Roi-ha and Parasite actor Song Kang-ho) are immediately overwhelmed by the shocking magnitude of the crime, as well as their own lack of experience and personal ethics. Loosely based on the real-life story of South Korea’s first serial murders and set during the military dictatorship in 1986, Bong Joon-ho’s second film begins with a shocking scene: two woman have been raped and killed in the small rural town. In fact, it often ranks amongst the best films of the past century, and is a mainstay in other directors’ all-time lists Quentin Tarantino even called it “one of the most interesting and complex movies” of the 21st century, and “a masterpiece”. Long before Parasite won him an unexpected Academy Award, Memories of Murder was the film that shot director Bong Joon-ho to international acclaim. He drifted away to Paris after Nazi propaganda minister Joseph Goebbels offered him the biggest job in German cinema M stands as a portrait of a country about to lose its innocence.

It was the last to be released in his homeland too. There's an economy and poetry to M – see the opening sequence in which young Elsie is lured away by Beckert with a balloon – which perhaps explains why it was Lang's favourite of his own films.

He set a trend among movie serial killers to follow too, in questioning the moral authority of the people sitting in judgement on him. Peter Lorre's breakout role as killer Hans Beckert used his soft, sad eyes to make him an especially unsettling bad guy. Fritz Lang's first talkie was also one of the first procedural police dramas, but it came with a couple of twists: it's not just the police on the tail of the killer, but the criminal underclass too and we know exactly who the murderer is from the very beginning. In Weimar era Berlin, there's a child-killer stalking the streets.

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