The body of 92-year-old Jossi Goldberg, Holocaust survivor and American citizen, is found shot to death execution style in his house near Frankfurt. A five-digit number is scrawled in blood at the murder scene. The autopsy reveals an old and unsuccessfully covered tattoo on the corpse's arm - a blood type marker once used by Hitler's SS. Kirchhoff and Bodenstein are faced with a riddle. Was the old man not Jewish after all? Who was he, really? Two more, similar murders happen and slowly the connections between the victims becomes evident.