Prof. Karl-Friedrich Boerne is on his way on vacation. But he was still in the testing phase, in full diving gear in the middle of his living room, when Mona Lux's body was found in the "Swan Lake" therapy center. At the bottom of the in-house swimming pool and weighed down with weights. And Andreas Kullmann, who did his laps there like every morning, doesn't want to have noticed the dead woman. Difficult to imagine, finds Inspector Frank Thiel. But "Swan Lake" is a psychiatric facility and Kullmann is autistic. Although the circle of suspects is small, the situation is confusing.
As Silke Haller, alias Alberich, imIf the blood of the dead finds a strong narcotic, Boerne of course does without his vacation: How can this case be solved without his help? He meddles arbitrarily as a therapist with the "Swan Lake" patients. But he doesn't find out about the dead person any more than commissioners Thiel and Nadeshda Krusenstern. Mona Lux had no family, no address, and might not even be called Mona Lux. But she was involved with restaurant owner Alberto DiSarto, who is under investigation for serious tax fraud. And Nadeshda Krusenstern can't shake the feeling that she has seen Mona Lux before...