Joan Bakewell explores the moral ambiguity of Oskar Schindler, the saviour of more than 1,200 people but also a Nazi and notorious black marketeer. Using interviews with Thomas Keneally, author of Schindler's Ark, and some of the people Schindler saved, this programme explores the nature of heroism. Half a century after the events, the survivors ask why the lessons of the Holocaust are still to be learnt.