The continuing story of the diehards committed to hunt down thousands of Nazi war criminals, some of whom were living in plain sight. One such woman was German Beate Klarsfeld, determined to right the wrongs of her country's dark past and identify Nazis who had gone unpunished - including the notorious Klaus Barbie. The documentary also tells the story of Josef Mengele - who performed gruesome experiments on Auschwitz inmates - and the son so appalled by his father's actions he considered turning him in