Last week's Vienna Blood ended on the revelation that Reinhardt and Max are chasing a serial killer. They have some clues as to who it is already. He's a soldier, a nationalist, who is either part of or inspired by the Brotherhood of Primal Fire. His victims so far are prostitutes, women of color, and immigrants. This week's episode opens with Max attempting a date with Amelia Lydgate, insisting he's just thanking her for helping them on the case. But she is no fool and tells him point-blank they should not see each other again. She also wishes him a pointed "Good luck" with his engagement to Clara.
Clara: I didn't realize there were three of us. That's going to make it awkward when we have to choose a dance partner.
So Max takes Clara on a date. She believes it's to see a lovely art opening. But the artist in question turns out to be Olbricht, who begs Max to "keep a muzzle" on Reinhardt. Once she sees the Inspector, Clara realizes this is no date and walks off. Max gravitates towards one of the soldiers, Ruprecht Hafner (Laurence Rupp). Hafner says he's just here for the champaign, his uncle, Gustav von Triebenbach (Mendel's investor from last week), is the real art-lover. He's not impressed with Max when he hears the Jewish last name, but he's all over Clara.
Max is having a bad week in general. Not only does Clara now have a new suitor (Hafner showing up at her house with flowers), but Professor Gruner bins his work with Herr Bieber, and takes the case away from him, electrocuting the patient. Moreover, he has to break it to his father von Triebenbach's nationalism is not something he stumbled across but a deeply held belief. Mendel decides he cannot accept the investment, telling his wife that the finer things she'd hoped for must wait. But Rachel is smart and resilient. Max may be insufferable, but his family is good people.
And then a third body turns up in the sewers with the Brotherhood rune symbol painted on the wall. Reinhardt has to break it to Strasser that every single immigrant in the city should now be considered in danger. As thrilled as he is to keep working on the case, the body makes Max late to pick Clara up for The Magic Flute. She's so pissed they're nearly late for curtain, she doesn't tell him about Hafner's visit. If that's not bad enough, the opera's plot gives Max PTSD flashbacks to the case. He drags Clara out of the theater and over to Reinhardt's, where he spells out his realization. Each murder is re-enacting The Magic Flute, scene by scene. Clara is shocked. But at least Max is (finally!) letting her see his work.
Von Triebenbach is the only link to the Brotherhood, so Reinhardt and Max confront him with their evidence. He declares all of this absurd, but Sgt. Haussmann turns up a photograph of von Triebenbach with a group of nationalist soldiers standing in front of a shield with the rune on it. Meanwhile, Mendel breaks their contract, much to von Triebenbach's shock. "No one throws me out." Mendel responds, "Well, then, this has been a new experience for you."
Clara asks Max to tell her more about the case, and he admits he thinks the killer is Hafner. Blessed girl, Clara decides she will trap Max's suspect herself and invites him over. Hafner arrives at Clara's house (where are her parents?), to find her dressed as a nymph goddess. But Clara is shocked as Hafner locks the door, and a horrific rape scene begins. At home, Max gets a note from Clara detailing the plan, and races over, arriving just in time. He punches Hafner in the face, only to be challenged to pistols at dawn.
Max runs to Reinhardt, demanding Hafner be arrested for what he did to Clara. Reinhardt looks at him as if he's mad. It's 1907; she invited him in, her reputation will go down. But the duel is a perfect place to get a confession. Reinhardt can't be Max's second, Hafner knows his face. But he's never met von Bulow, making Reinhardt's rival the perfect undercover officer for the job. They'll even give him the collar if he agrees. There's just one problem: Hafner isn't the killer. The real murderer is shadowing them and knocks out Reinhardt on his way home.
At the duel, Hafner is insulted at Max's accusations. His trips to the brothel were only ever with a friend. He won't say who, but Max starts putting two and two together once he realizes Oskar is missing. The killer is Olbricht, who was also a soldier once, and whose nymph painting are all an idealized image of his mother. He's cast Oskar as the next part in the play: The policeman.
Max finds Reinhardt tied up under the stage as the orchestra warms up. Under questioning, Olbricht admits, as a child, he saw his mother raped by an immigrant soldier, The Magic Flute was playing at the time. The job triggered his violent outbursts; the deaths are him trying to drive the memory away. Max knocks Olbricht out, accidentally setting off the rigging, hanging Olbricht upside down over the stage, in a picture-perfect capture.
With the case solved, Max tries to thank Clara for what she did, telling her she's brave. But she won't let him touch her. Instead, she accuses him of wanting someone else. He admits he doesn't know what he wants. She declares that she for once knows him better than he does, and she's brave enough to end this relationship and throws him out.