Dan Reed ("Leaving Neverland") discusses his new FRONTLINE documentary, "In the Shadow of 9/11," the story of how seven Black men from Miami were accused of planning an Al Qaeda plot to blow up American buildings.

As the nation marks the 20th anniversary of Sept. 11, the legacy of the terror attacks and their aftermath continues to unfold, from insurrection at the U.S. Capitol to the resurgence of the Taliban in Afghanistan.