Joseph Mengele - the escaped Nazi war criminal and SS physician known as the Angel of Death - spent years doing bizarre medical experiments on twins at Auschwitz, working to determine if twins held the key to building a blonde-haired, blue-eyed master race for Adolf Hitler. Now a historian says he has evidence that Mengeles attempts may not have ended at Auschwitz and that his obsession to engineer an Aryan master race continued in South America. Deep in the Brazilian outback, a tiny town exists with reportedly some 44 pairs of twins, maybe blonde and blue-eyed. Could they be the product of Mengeles machinations? with exclusive access, National Geographic goes inside the investigation. From the secret agents who trailed him, to the scientists now uncovering the facts behind the fantastical phenomenon, no stone is left unturned.