In twentieth-century Germany, Karl-Friedrich Bonhoeffer rose to prominence as a brilliant physical chemist, even as several of his relatives—Dietrich Bonhoeffer among them—became involved in the resistance to Hitler, leading to their executions. This book traces the entanglement of science, religion, and politics in the Third Reich and in the lives of Karl-Friedrich, his family and his colleagues, including Fritz Haber and Werner Heisenberg. Nominated for the Nobel Prize, Karl-Friedrich was an expert on heavy water, a component of the atomic bomb. During the war, he was caught in the middle between relatives who were trying to kill Hitler and friends who were helping Hitler build a nuclear weapon. Karl-Friedrich emerges as a complex figure—an agnostic whose brother was a renowned theologian, and a chemist who both reluctantly advised German nuclear scientists and collaborated with Paul Rosbaud, a spy for the British. Illuminating the uneasy position of science in twentieth-century Germany, The Scientific World of Karl-Friedrich Bonhoeffer is the story of a man in love with chemistry, his family, and his nation, trying to do right by all of them in the midst of chaos.