Powers, an experienced journalist and writer, makes the case that Nobel laureate Werner Heisenberg acted to slow down and ultimately block German development of a nuclear weapon during World War II, resisting the Nazi regime from within. Perhaps, but to his credit, he admits that others, looking at the same body of evidence, have legitimately drawn different conclusions. It is, at the very least, quite clear that Heisenberg was willing to assume a comfortable place in an evil regime, when others chose different courses of action. The book's chief weakness, and a major one, is that Powers does not appear to know German, although he had the aid of a German-speaking assistant who translated documents and conducted interviews. As a result, the book relies very heavily on American sources from the Office of Strategic Services who were monitoring the German effort, hoping to stymie it during the war and learn from it afterwards. That is, in fact, part of the book's interest. An engrossing tale, superbly told, about a man who, appropriately enough, gave the word "uncertainty" a significance that reverberates to the present day.