The night before his marriage to Sandra Mangold (Nele Mueller-Stöfen), the head of department at the Berlin pharmaceutical company NOVOFACT, Prof. Eugen Jähnicke (Walter Kreye), head of the institute for animal experiments, VIVITEST, is found murdered. The cause of death is a mystery, but one thing is clear: his death was "arranged". The dead professor lies on the dissection table in his institute's animal pathology department like one of his test animals: his stretched-out body is full of cannulas, probes, hoses and electrodes. The commissioners Till Ritter (Dominic Raacke) and Felix Stark (Boris Aljinovic) suspect that the perpetrator wanted to set an example and is to be found in the circles of animal experimentation opponents.
Even Jähnicke's own stepdaughter Caro (Karoline Teska) is suspected, especially since the radical animal rights activist had just had a physical argument with him. And then there is Ingo Kaiser (Axel Neumann), who loudly suspected the professor of stealing his beloved cat Manou for animal experiments. But there is also a lot to research in the private life of the professor, because the good-looking widower tended to have affairs. His last lover was his colleague, the head of the animal testing series, Dr. Claudia Knobba (Sheri Hagen), before deciding to marry the attractive Sandra Mangold - for Dr. Knobba a bitter disappointment.
Was it maybe a murder out of jealousy? But Sandra is also suspicious: Ritter catches her in Jähnicke's sealed office while she is in the process of deleting computer files. And the professor himself destroyed documents in the shredder shortly before his death. What story were the research institute and the pharmaceutical company involved in? Did Prof. Jähnicke have to die because of this? And what role does Volker Bensch (Volker Bruch), who works in the institute as a laboratory animal keeper and apparently also has good contacts with animal rights activists, actually play? While Ritter and Stark are feverishly investigating, the situation in the Jähnicke house escalates.
Caro and the longtime housekeeper Margarete Baier (Jenny Gröllmann), who raised her almost like a mother, leave the villa after an argument – her relationship with Sandra was never the best anyway. They even suspect each other of having something to do with the professor's death. But then Ritter and Stark discover a hot lead - and they owe it not least to the two lovebirds, also known as the "lovebirds", who the professor kept in his office.