A highly secret Pentagon intelligence unit was tracking Osama Bin Laden in 2000. They knew the targets included the World Trade Center and the Pentagon. They suspected the use of planes to fly into buildings. They were told to fold their tent by higher-ups. A later Inspector General investigation, prompted by the protests of one of the intel unit’s leaders, covered up what really happened. But newly released documents are finally allowing the contours of the full story to come out.