As Iraq descends into chaos and civil war, Frontline examines the rise of its neighbor - Iran - as one of America's greatest threats and most puzzling foreign policy challenges. Through interviews with key players on both sides, Frontline traces the tumultuous history of U.S.-Iran relations since 9/11 - from unprecedented early cooperation in Afghanistan to the growing crisis over Iran's nuclear ambitions and Tehran's open threats to drive America out of the Middle East.

Tuesday, 10/23/07 from 10-11 p.m. ET