The first hint of calamity came in deceptively routine form: a small fire in a rented Carson warehouse, apparently sparked by welders working on a lunch truck. But an investigation of that blaze turned up alarming details: respirators, a suspicious hookup on the truck, large sacks of rice flour. Within weeks, those puzzling discoveries would plunge Los Angeles into a whirlwind as a routine fire probe rapidly spun into an international investigation, uncovering a terrorist weapons lab in Mexico and a plan to douse the nation's second-largest city with anthrax and ricin. By the 40th day of the crisis, panic-stricken...