Amelia has determined that the only way Countess Nadazdy could have been poisoned is via the water for her tea—the Countess was too careful in her diet and Amelia has not been able to find a trace of strychnine anywhere else. Whoever poisoned the countess had to have gotten very close to her, while pouring her tea.
So Oskar arrests Oktav Hauke, who danced and ate dinner with the countess just before she died. But Oskar’s suspicions crumble when he questions Hauke: the former soldier wasn’t in the countess’s will, so he didn’t stand to gain anything from her death. Furthermore, they were just companions, not lovers. An exhumation of Hauke’s former landlady shows no trace of poison either. Hauke is let go.
Under pressure from his disliked boss, von Bülow, Oskar asks Max to find a lead in his sessions with the countess. Max looks into “Blanka Mar,” a name the countess would mention when she became upset. Max assumed she was a fantasy, but perhaps she’s real. Except Fraulein Lindner, the police archivist, can’t find a trace of her.
Meanwhile, Oskar searches for more clues at the hotel. He learns from one of his subordinates that the hotel seems to offer its porters up as sexual partners: a “menu” of options was found in one of their rooms.
After Max’s notes on the countess disappear while he is working at the hospital, he devises a plan to catch her killer, who must think Max knows their identity. Max can be bait. He waits late at night at his practice until a man enters threateningly. Oskar intervenes when things get dicey, but it turns out the man is simply the suspicious husband of one of Max’s patients, who wants to know what she tells Max.
Max’s father tells Max that his former fiancée Clara is newly engaged, and encourages Max to start a relationship with another eligible woman, explaining that a parent never stops worrying about their child.
Max rushes to Oskar with a revelation: the countess had a child! The nightmare she related referenced the child and her guilt over abandoning it. The person close to her whom she feared was her child.
The countess’s maid confirms Max’s suppositions. The countess’s son, István, was spoiled but eventually became twisted and did terrible things, like disfiguring another child—Blanka Mar. István was sent to a sanitarium in Vienna when he was 9. His doctor and Blanka’s family were paid to keep silent; all records were destroyed, István’s existence wiped out.
István was eventually transferred to a different sanitarium. He recently escaped. That’s why the countess feared for her life. The existence of her lost son also explains her attraction to Hauke, a younger man: she was spoiling him as displacement of her feelings about her son.
Max is now even more intent on meeting and catching István. Sensing that he is being followed one night, he turns around and chases his follower, who flees into a park. Max is accosted by a man and tries to convince him he can help him—but it’s not István. The man robs Max of his coat, hat, and wallet.
The next day, the man is found dead, stabbed to death in the park. István must have attacked him thinking he was Max. Oskar is done gambling with Max’s life, but Max still wants to use himself as bait to reach István.
Then Max finds another clue leading to István. Asking the name of a bellboy while at the hotel, he realizes it’s the same name as the one who came to him with jewelry from the countess even though they are different people. The one who came to him must have been István, scouting out Max. He then returned later to ransack Max’s practice.
Returning to the countess’s maid, Max asks her to identify István’s original doctor in Vienna: it’s his rival Grüner. Under pressure from Oskar, Grüner admits that he erased István’s records. He has never observed anyone like István, who attacked another boy in the children’s wing of the sanitarium, now closed.
Max and Oskar go to the shuttered wing, the site of the countess’s nightmare. Max finds István and tries to help him despite the knife he brandishes. István says he didn’t kill his mother, though he wanted to for years. He watched her with Hauke and yearned for such a relationship himself. As Max tries to coax more out of him, István slices Max’s hand and Oskar rushes in and shoots the boy in the shoulder. István is arrested, but Max believes him that he’s not the killer: he couldn’t have reunited with a dead mother.
While Oskar and Max have a drink at a café, the waiter knocks Oskar’s coat off a chair and replaces it, and Max has a realization. The hotel director replaced the countess’s shawl on her chair while she was dancing the night she died—what if he put it on the wrong chair? What if Hauke was the target of the poison, not the countess?
Fraulein Lindner finds news of a soldier in the same regiment as Hauke who hanged himself after being found in bed with another soldier who was summarily dismissed—presumably Hauke, although his name was withheld.
Oskar realizes that Hauke was at the hotel not to seduce wealthy older women but to partake in its clandestine sexual offerings. Max recalls that the hotel’s housekeeper mentioned having a son who was in the same regiment as Hauke. They rush to the hotel, where Hauke is with one of the porters, dressed up all in white, like the “evil” veiled woman the countess and another guest noticed walking the halls. But they’re too late: the housekeeper shoots Hauke and then herself after Hauke says that he and her son loved each other. She tried to poison Hauke for, in her belief, causing her son’s death, but accidentally poisoned the countess instead.
Max’s name has been cleared; Grüner is now the one facing a disciplinary hearing. And Max has been asked to be a witness.