With his customary reportorial brilliance, John McPhee has written the story of the life and career of Theodore B. Taylor, a theoretical physicist who has been one of the most inventive nuclear scientists of our time. He miniaturized the atomic bomb, and also designed the largest-yield fission bomb that has ever been exploded. Subsequently, he led a scientific effort to build a nuclear-powered spaceship. But he later became convinced that weapons-grade uranium and plutonium are alarmingly available to anyone who might wish to build a homemade bomb, and that such an undertaking would not be impossible, as some think. Taylor for many years has tried to effect improvements in the protection of nuclear materials, in the hope of averting their catastrophic use. McPhee's exploration of Taylor's world provides a timely look at a central aspect of the history of nuclear energy, and the assessment of one of its risks.