On the tenth anniversary of the tragic events of September 11, FRONTLINE rebroadcasts the extraordinary saga of FBI special agent John O'Neill. As the bureau's top counterterrorism agent, O'Neill - who investigated the bombings of the U.S. embassies in Africa and the attack on the USS Cole - joined then national security counterterrorism co-coordinator Richard Clarke in believing that the United States should kill Osama bin Laden before Al Qaeda launched a devastating attack on America. Richard Clarke, then speaking in his first major interview, talks about O'Neill's battles with the FBI top brass who found O'Neill's James Bond style an anathema. Forced out of the job he loved, O'Neill took a new position in the private sector - as head of security at the World Trade Center, where he was killed on September 11. The story of O'Neill's life and death provides a rare glimpse inside the FBI and helps answer the question: What did the government know?