Over the last three years, FRONTLINE has collaborated with ProPublica to investigate the rise of extremism in America. In the aftermath of the Jan. 6, 2021 assault on the U.S. Capitol, FRONTLINE, ProPublica, and Berkeley Journalism's Investigative Reporting Program team up to examine how far-right extremist groups have evolved in the wake of the deadly 2017 Charlottesville rally — and the threat they pose today.