One day in 2002, three friends-a Somali immigrant, a Pakistan-born U.S. citizen, and a hometown African American-met in an Ohio coffee shop and vented over civilian casualties in the war in Afghanistan. Their conversation triggered an investigation that became one of the most far-reaching government probes into terrorism since the 9/11 attacks.

One day in 2002, three friends - a Somali immigrant, a Pakistan-born U.S. citizen, and a hometown African American - met in a Columbus, Ohio coffee shop and vented over civilian casualties in the war in Afghanistan.