Elder Paul Seibach has been working as a security carrier for a supermarket for a year. One day, waiting for him at the exit, the man finds a masked thug who, after robbing him, manages to escape. Back home, Seibach shows up at the door of his neighbor, Harald Rohn, claiming to have recognized him as the perpetrator of the robbery. That same evening Derrick is called to the crime scene: Seibach's body lies on the road in front of the house and his children, Lena and Eugen, cannot explain their father's tragic death.