There was documentary called "The Road to 9/11" where a former FBI agent (Mark Rossini) said (paraphrasing) "I tracked a known terrorist - a man on our no-fly list - from Singapore to San Diego. When he was in San Diego, I notified my bosses. After a few days, I asked for an update. I was notified by the CIA to walk away. They were tracking him. They wanted him in the country to 'observe his movements' and 'his associates.'"

In a written interview, Rossini said the following:

“There’s every reason to believe, circumstantially, that the Saudis were trying to recruit from the middle of the terror cell with the help of the CIA or the permission of the CIA. The reason why [my memo] was suppressed was because the CIA was working with the Saudi intelligence service; circumstantially everything points to that. It’s not conspiracy. It’s just logic. [The CIA] gave them a free hand to recruit or investigate or contact these boys that were coming to the U.S. to find out what they were doing and what they were up to,”

Immediately after 9/11, the story was that "we had the info, but we couldn't connect the dots" and that rivalry between the CIA and FBI caused an intelligence failure. I believe the origin of this fan-fiction was based on Rossini's true story. He alerted people about this terrorist - and was told to back off by the CIA. But here is where reality diverges from fiction: the CIA didn't want to arrest the terrorist to win the "agency rivalry." They wanted to 'observe' the terrorist as he acted freely in our own country. That isn't an intelligence failure - that was by design.

Rossini appears to be a good guy. But he was a good guy at the wrong time - a time where the DS finally outnumbered the good guys in key positions and showed the world what they would do.