Max and Oskar both face difficult emotional situations. Oskar attends the burial of Viktor Krull and apologizes to Viktor’s mother for his death, receiving a slap in return. He understands; he, too, has had to bury a child.
Max goes to see Amelia Lydgate at the museum, and she tells him that their acquaintance should end, given that she’s trying to rebuild her life after her illness and he is engaged—not so happily, we might add. Max’s fiancée Clara cheers up after their recent argument when Max invites her to an artist’s show, but she is once again disappointed: Oskar is there, too, and he and Max are there to look into the racist Brotherhood of Primal Fire, which seems to be involved in a spate of recent murders.
After Clara leaves Max to convene with Oskar, they begin moving through the show. Max speaks with an arrogant young soldier who says he is a friend of the artist Olbricht and a nephew of the host, von Triebenbach—the investor in Max’s father’s business who gave him the Brotherhood’s Aryan pamphlet. The soldier doesn’t repay Max’s courtesy of introducing himself.
He does, however, reveal his name—Hafner—to Clara, when he tries to flirt with her and is dismissively turned away. Meanwhile, Max turns his attention to von Triebenbach, asking if he is the author of the pamphlet. The businessman unconvincingly responds that Max must be mistaken.
After the art show, Max warns his father that von Triebenbach might be more sympathetic to the Aryan cause of the pamphlet than he suspected. Herr Liebermann decides that, as a liberal Jew, he can’t accept money from such a man. He cancels the contract with von Triebenbach—the investor isn’t happy, and references the danger Liebermann could be in as a Jew.
Later, Clara excitedly opens her house’s door to a bouquet of flowers. Since she is waiting for Max to take her to the opera, she believes it’s him—but instead Hafner steps out from behind the blooms. She speaks with him, he confidently disparages Max, and he leaves after making an offer for her to come to him when she tires of her fiancé.
Max is delayed in picking up Clara. He is busy psychoanalyzing Bieber, the bookkeeper who believes the Archduchess is his lover. Max determines that Bieber has a “primal fear of sex,” probably from something he witnessed as a child, and recommends a talking cure, a la Freud. But his professor disagrees with Freud and takes the case from Max. Later, Bieber is dismissed from the hospital: the professor “made me forget,” he tells Max, presumably with shock therapy.
Max is then called to another murder scene: an African man in the sewer, once again marked with the sign of the Brotherhood of Primal Fire. The killer is targeting outsiders and immigrants.
When Max finally arrives at Clara’s, she is upset by his tardiness. They get to their seats during the overture of the opera: The Magic Flute, with sets by Olbricht. Having annoyed their seatmates once by arriving late, they do so again midway through by leaving early. Max has had a realization, and asks Clara to come with him.
They go to Oskar, and Max explains his epiphany. The killer is retelling The Magic Flute. First, there was the mutilated snake found in the zoo near a statue of Mozart, a match to the serpent seen at the start of the opera. Next were the three prostitutes, analogues to the three servants of the queen of the night. Then the Czech poultry seller: Papageno the bird-catcher. And finally, the African in the sewers stands in for Monostatos the moor.
Suspecting von Triebenbach, Oskar and Max go to interrogate him. Although they find a photograph of him with several soldiers, including Hafner, and the symbol of the Brotherhood, he claims he’s not responsible for the murders, and they have no evidence.
When Clara, curious about the case now that she has heard Max discuss its connection to the opera, asks Max if the killer has been apprehended, he says no—but he knows it was Hafner. He just can’t prove it. After Max leaves, Clara sits down to write two letters: one to Max, and one to Hafner.
Soon, Hafner is strutting into Clara’s home. She wants to help the investigation, but has severely misjudged Hafner’s capacity for violence. Rejecting one aggressive advance, she asks to converse, then makes the mistake of saying they are alone. He locks the door, forces her onto a couch, holds her down, and begins undoing his pants after ripping her dress. This horrible scene is luckily interrupted by Max kicking open the locked door—he rushed over as soon as he received Clara’s note sharing her plans.
Hafner boldly gets off Clara and puts his belt back on, insulting Max and his “impotence.” Max hits him; Hafner takes offense and challenges him to a duel at dawn the next day before striding away.
When Max asks Oskar to arrest Hafner, Oskar says he can’t: the misogynistic justice system would not stick charges on Hafner, since Clara invited him over. So Max decides to go to the duel and get Hafner to confess to the murders. He needs a second, both for the duel and as a witness for the confession, but Hafner knows Oskar is a policeman, so he decides to take Oskar’s rival, von Bülow. Oskar will be on hand but out of sight for added security.
Except Oskar is followed and attacked from behind in the streets, so he doesn’t show up.
As Max and Hafner walk their paces, Max congratulates Hafner on the cleverness of his references to The Magic Flute with the murders. After more such needling from Max, Hafner abruptly turns and yells, “I’m not the murderer!” Max asks about the brothel; Hafner admits to going but that a friend took him there. Max suddenly realizes that friend must be Olbricht, the artist, and runs off to tell Oskar—but he’s nowhere to be found.
Fortunately, Max has figured Olbricht out, and guesses—correctly—that he has taken Oskar to The Magic Flute. Olbricht has tied Oskar up and gagged him under the stage, looping a rope around his neck. As the overture starts, Max breaks in with another policeman, whom he sends away so that he can negotiate with Olbricht. Having realized that Olbricht’s mother is in all of his paintings—and perhaps with a hint from the case of Bieber—Max asks the artist what happened to his mother when he was a boy.
She was assaulted by a soldier—and The Magic Flute was playing the whole time. Olbricht is trying to exorcise his memory of the trauma by killing off all the characters in the opera. Hence Oskar, who can stand in for Sarastro as an arbiter of justice. Olbricht becomes emotional; Max knocks him down; and the prop snake (made by Olbricht) begins to be pulled up to the stage. Max unwinds the rope from Oskar’s neck before he is hanged, while Olbricht is dragged upside down over the stage—his foot has caught in the rope.
Max later goes to Clara to tell her the case is over, and to laud her for her bravery. She replies that she will again show bravery by ending their engagement—it’s clear it’s a mistake. All she asks is who the other woman is, and whether Max loves her. Unfortunately, he doesn’t know himself.