The Hunt For The Anthrax Killers

In a conference call with workers last Wednesday, the day Manhattan employees started taking Cipro, William Burrus, incoming head of the American Postal Workers Union, tried to introduce his colleagues to their new job descriptions. "In a war, there are casualties," he told some 15,000 postal workers listening around the country. "In the past, we've viewed wars on television, and they've been sanitized and far away. But we are the battlefront now."

As those newly drafted civil soldiers returned to work, investigators raced to protect them from more enemies they can't see. Late last week a fragile consensus was emerging among intelligence sources that the culprit is likely a lone scientist in our midst, someone who has no connection to Osama bin Laden--except for a shared talent for terrifying Americans.

--Reported by Anne Berryman/Atlanta, Andrea Dorfman and Alice Park/New York, Andrew Goldstein and Elaine Shannon/Washington and Jeffrey Ressner/Los Angeles, with other bureaus