The Cabinet of Dr. Caligari
This film is often touted as an "expressionist" film, but I would rather describe it as a horror film.
It was made in 1920, between the two world wars, and was originally to have been directed by Fritz Lang of Metropolis fame, but was given to Robert Wiene instead.
It is the story of a director of an insane asylum who also doubles as a hypnotist and gets a somnambulist to commit murders during the night.
At its most basic level, this film predicts the infamous Nazi method of making sleep walkers out of the people, convincing them (or hypnotizing them) to commit their bliztkriegs on humanity.
On another level, it anticipates the great Nazi propaganda machine which uses art at its most banal to create its ghouls which would assist it in its horrors.
The film actually makes the viewer into an accomplice. It is itself hypnotic. We enjoy the movie.
At the very end, no real justice is reached since all the characters are part of an insane asylum. We sympathize, and even associate, with these residents. They are stuck behind the formidable forces of their minds and the asylum's walls.
Rather than arrest this mad doctor, the witnesses cannot get out of their trance. They are after all, part of this asylum which he directs. And he is their director (their Fűhrer).
There is no way out but to depend on him. They are unable (too complacent) to jolt themselves out of their fabricated madness and his influence.
At the final apparition of the director, he actually looks benign and composed (unlike his hypnotist days). We (spectators/viewers) even get to trust him a little.
The German people were slowly getting hooked.