He was one of the most notorious Nazi war criminals, infamous for his deadly experiments on twins. But at the end of WWII, he simply disappeared. Despite a global manhunt by Mossad and the allies, he would die a free man, 34 years later, in Brazil. Who was Dr Mengele? What did he do after the war? And why was he never caught? We speak to those who knew him and profile the 'angel of death'.