Diabel (The Devil)
The Stranger/The Devil kills Jakub after Jakub signs a document confirming the identities of all those who conspired to kill the king. After the Stranger tries to rape the Nun, she castrates and kills him. The Stranger turns into a wolf upon dying.
This film was banned in the director's native Poland for years, accused by the authorities of criticizing the government and the Church.
The movie opens in the midst of the Prussian invasion of Poland in the 1790s. A Stranger clad in black (Wojciech Pszoniak) enters a prison where Jakub (Leszek Teleszynski) is being held on charges that he tried to assassinate the king as part of a conspiracy. The Stranger frees Jakub in the midst of a riot, tells him to return home, and sends a white-clad Nun (Monika Niemczyk) to accompany Jakub. The Nun appears to be a representation of goodness/god and the Stranger a representation of evil/the Devil. Through most of the movie, the Nun remains in a state of stunned horror at the things she and Jakub witness.
Along the way, Jakub (who is constantly followed by the Stranger) encounters a hedonistic group of actors, all of whom wish to seduce him. He finds that his best friend and co-conspirator told Jakub's pregnant fiancée that Jakub was killed and has married her instead (it also appears that Jakub's friend is now working for the King). Jakub returns home to find that his father committed suicide, his sister has gone mad. The household is being run by his half-brother, who mocks Jakub's cause and intends to marry Jakub's sister (whom he mercilessly beats). Jakub also learns that his mother (who abandoned Jakub and his sister as children) actually has lived close by their entire lives, running a bordello. He confronts his mother at the bordello (the mother does not appear to recognize Jakub) where they almost sleep together (intra-family sexual taboos are a theme throughout the film. The sister is betrothed to her half-brother and was seemingly raped by their father after the father went insane. Jakub appears to have romantic feelings for his mom and sister). Jakub takes out his rage on another prostitute, slitting her throat with a straight razor given to him by the Stranger.
Repulsed by his actions, Jakub seeks comfort from the Nun, but she pushes him away. Jakub appears to go mad. He returns to his friend's castle to try and reunite with his fiancée, only to be beaten (and then, kissed) by his former best friend. He is found by the acting troupe and is seduced by one of the actresses. In mid-coitus, he is attacked by another actor out of jealousy. Jakub kills the actor and actress and is pursued by the remaining troupe. The leader of the troupe (a man) tries to sleep with Jakub in exchange for not turning him in to the authorities. The Stranger shows up and saves Jakub by killing the leader of the troupe. He then has Jakub return to his mother's bordello.
The mother embraces Jakub (now knowing who he is) and takes him to the basement where the denizens are engaged in all manner of hedonistic actions. She says he can stay with her as a prostitute, where people will be thrilled by any murders he commits. She also claims that the Stranger is a low-level government clerk. Having seemingly taken the Stranger's earlier claims that Jakub is meant to cleanse the world at true, he kills his mother and disperses the crowd. He then returns home where he kills his step-brother, mercy kills his sister (who had been horribly beaten by their blood-thirsty half-brother), and burns down his family house. He reunites with the Nun and though he makes a pass at her, the two do not have sex.
They journey to a place he played as a child to find his ex-fiancée there. She expresses a wish to run away with Jakub, but then passes away due to complications with her pregnancy (and passes away despite Jakub pleading with the Nun to save her). Enraged, Jakub returns to his best friend's home and kills his friend in a duel. Delirious from his ordeal, the Nun helps Jakub flee into the woods where they are encountered once more by the Stranger. The Stranger demands Jakub sign a document identifying all his former friends and family as conspirators against the king and crediting the Stranger with bringing the conspiracy down (this seems to confirm the Mother's claims that the Stranger is indeed a man working for the government). The Stranger says he had to expose Jakub to the truth about his family and friends or else he never would have given them up. Jakub agrees to sign only if the Stranger can tell him if the world has beauty in it or if it is all corrupt. The Stranger says the world is beautiful (and portrays his feelings through dance). After Jakub signs the document, the Stranger fatally shoots him in the head and takes the Nun.
The pair journey to some Prussian soldiers where the Stranger hands them the documents signed by Jakub. The soldiers criticize the stranger as immoral, pay him for his work, and mock his interest corrupting Jakub's soul. Enraged, the Stranger attacks and starts raping the Nun. She uses the opportunity to steal the Stranger's straight-razor and castrates him. The Stranger turns into a wolf (suggesting he really was the Devil after all) and dies from his wounds. The film ends with the Nun standing victorious over the canine-corpse of the Stranger.