FRONTLINE goes behind the mounting debate over the Bush administration's domestic eavesdropping program and the FBI's disputed use of national security letters to examine whether the administration's domestic war on terrorism is jeopardizing our civil liberties. Reporter Hedrick Smith takes viewers inside the National Security Agency's domestic surveillance program to show how it works, presenting opposing views over whether this program clashes with Fourth Amendment constitutional protections of individual privacy. In another dramatic story, the program shows how the FBI vacuumed up records on 250,000 ordinary Americans who chose Las Vegas for their Christmas-New Year's holiday, and the subsequent revelation that the FBI has misused National Security Letters to gather information. Probing such Pentagon projects as Total Information Awareness - and its little known successors - Smith discloses that even former government intelligence officials now worry that the combination of new security threats, modern computer and communications technologies, and radical interpretations of presidential authority is affecting innocent, ordinary Americans and may be threatening our liberties.