In the deep midwinter of 2002, FBI divers cut holes in the ice and then searched several ponds near a Fort Detrick, Md., biodefense lab for evidence in the anthrax investigation. It was an expensive, cinematic strategy that would ultimately lead nowhere, but no one knew that then. Except perhaps for the older man who stood off to the side handing out coffee and sandwiches. In addition to being a respected scientist, Bruce Ivins was a Red Cross volunteer, manning the canteen. He was known as reliable and cheerful, and he had been asked by the Frederick County,...