At a crime scene in the zoo, detectives Tessa Ott and Isabelle Grandjean experience a surprise: the victim is a chimpanzee. Although public prosecutor Anita Wegenast classifies the terrible act as damage to property in a formally legally correct but morally questionable way, Tessa, indignant, continues to investigate on her own. But little by little, more and more bodies appear in Zurich, which at first glance have little in common. There could also be a crime behind the disappearance of a suspect. The investigator Ott and Grandjean are forced to act. Only when they recognize a pattern in the actions can they solve the murder mystery. However, the fact that her careerist superior Wegenast, who is well connected and working on her promotion, wants to take advantage of the results of the investigation turns out to be a risky move in a political game...