Twenty years after the attacks that changed our world, we revisit the evidence and question the people at the center of the story.

The mastermind of 9/11 as in the sights of the U.S. government. Until he wasn’t.

The U.S. has Osama bin Laden in its crosshairs. Will it take the shot?

How Osama bin Laden went from the son of a tycoon to leader of worldwide violent jihad.

Police investigating an apartment fire in Manila uncover a plot to blow up a dozen airplanes.

More than 20 years after he took down a terrorist cell and testified in open court, Emad Salem is still in hiding.

Emad Salem is back under cover, and the cell is planning its next attack.

After the World Trade Center bombing in 1993, investigators scramble to round up suspects.

A former Egyptian army soldier decides to go undercover in Brooklyn.