"I want to report a murder." It was already late when a man named Sven Döring asked for admission to the Frankfurt Homicide Squad to make this report. Chief Inspector Conny Mey leads him into the office of her colleague Chief Inspector Frank Steier, the only room in which the light is still on. "My son has been in a coma for a year and I know that his girlfriend Mariam tried to murder him and that her colleague Seidel covered up this act," Döring complains. He seems extremely dangerous to the two commissioners. He seems to be planning something, maybe he wants to take revenge on the alleged perpetrator. Inspector Mey insists on driving to the young woman and protecting her, but "we are the murder and not the murder prevention commission," says Steier. A classic police dilemma.
As long as nothing happened to the girl, there is no police action against the potential perpetrator. Mey and Steier don't want to put up with it, but they investigate anyway and come across some oddities. Meanwhile, Sven Döring is playing his murderous cat-and-mouse game with the young girl and the police. The noose around Mariam's neck tightens and a deadly race begins.