One overcast Sunday morning Chief Inspector Susanne Meder (Marita Marschall) and her team are called to an insignificant-looking crime scene. Two uniformed police officers on their rounds spotted signs of a break-in, but when they went to investigate they were caught up in gunfight in a cellar next door to a jeweler’s shop.
As a consequence not only one of the intruders but also a police officer are left dead. Susanne comforts the deeply distressed woman police officer as best she can: Gerrit Rost (Nicolette Krebitz) was out on patrol with her superior officer, and from all accounts it looks as though she lost her head in this tricky situation... because the ballistic report confirms the terrible suspicion that Gerrit Rost herself, whether deliberately or by mistake, fired the shots that killed her colleague.
Susanne’s ex-husband, public prosecutor Rolf Meder (Thomas Bestvater), insists that the policewoman should be charged. But Susanne simply refuses to believe that this young woman, a single mother who is bringing up a little daughter with all possible loving care, could be involved in such a serious crime, a crime which would threaten her very existence. However, the evidence tells a different story. Not only did Gerrit Rost know the intruder - there is incontrovertible proof that she was having an intimate relationship with him. What's more, when Pit (Daniel Wiemer) is bringing Gerrit Rost in for questioning she manages to give him the slip, only to be caught later at Frankfurt Main Station together with the brother of the intruder, Norbert Kramm (Matthias Matz)... and a bag full of jewels from a number of recent robberies.
However, it later turns out that Susanne’s instinct did not completely deceive her, because Cem (Ercan Durmaz) makes a discovery during his enquiries which casts a completely different light on the whole case.