In the 1970s, the Pakistani scientist A. Q. Khan used his position at a uranium-enrichment consortium in the Netherlands to acquire the information and contacts he needed to help his country build nuclear weapons. Khan later turned his network into an instrument of proliferation, assisting would-be nuclear powers with basic plans and infrastructure. These stories have been told before, but Albright is on top of the material and conveys the underlying scientific and engineering issues with lucidity and authority. He sketches the links among Iran, Iraq, North Korea, and Libya and, more alarming, throws light on what al Qaeda was up to while it enjoyed sanctuary in Afghanistan. The book is particularly good at tracing the movement of technology and uncovering how proliferators circumvented export controls and confused intelligence agencies -- for example, by using split orders and complex payment schemes to obscure why and how particular components were bought and sold. At times, following this trail can be as challenging to the reader as it was to the agencies, but Albright is undoubtedly right to emphasize that specialist manufacturers, the best placed to pick up the signs of dubious enterprises, should be enlisted to keep watch.