The story begins with a letter from Albert Einstein to Franklin D. Roosevelt in 1939. The celebrated physicist warned the president that Nazi Germany was developing the makings of an atomic bomb. Roosevelt knew what would happen if Hitler got such a weapon. The president ordered a massive secret project to make sure the U.S. beat him to it. Scientists from all over the country were enlisted in the effort. Early in 1942 Enrico Fermi and a team of physicists gathered at the University of Chicago's Metallurgical Laboratory. Their goal was to develop a self-sustaining nuclear pile. This was the...