Science has always been capable of huge innovation, and frightening destruction. The life of one scientist encapsulates that tension more than any other - Fritz Haber. In this programme Chris Bowlby explores Haber's dramatic life, personal as well as professional, discovering how a Jew desperate to be a patriotic German, became a chemist of great creativity, but also of military power. Scenes from his life explore how he made his discoveries - including the fertiliser that fed the world, and the poison gas used in the First World War. We hear of his struggle for social acceptance, the suicide of his wife in protest at his war work, and finally his tragic death, shortly after expulsion from Nazi Germany. But he had left the most ironic legacy of all - research that gave the Nazis the basis for the gas used to murder millions in the Holocaust.