The government is building a highly classified facility to research biological weapons, but its closed-door approach has raised concerns. On the grounds of a military base an hour's drive from the capital, the Bush administration is building a massive biodefense laboratory unlike any seen since biological weapons were banned 34 years ago. The heart of the lab is a cluster of sealed chambers built to contain the world's deadliest bacteria and viruses. There, scientists will spend their days simulating the unthinkable: bioterrorism attacks in the form of lethal anthrax spores rendered as wispy powders that can drift for miles on...