Modern natural sciences transcend many boundaries: boundaries of knowledge, tradition, the conceivable, and even the morally permissible. Fritz Haber is one such boundary crosser, whose characterization and assessment have always been highly controversial. For some, he is the brilliant scientist, Nobel laureate, and far-sighted science politician, while for others he is seen as a ruthless science technocrat, whose ambition also cost him his family. This biography, based on extensive source material, paints a nuanced portrait of Fritz Haber and also depicts a scientist who is modern and tragic in many respects.