An investigation into America's increasingly bitter, divided, and toxic politics. Part One traces how Barack Obama's promise of unity collapsed as increasing racial, cultural, and political divisions laid the groundwork for the rise of Donald Trump.

This two-part hour includes "Taliban Country" and "The Luanda Leaks."

Taliban Country: Nearly 20 years after the U.S. drove the Taliban from power in Afghanistan, the group claims it holds more territory than any time since the war began in 2001. As President Trump says he wants to end the war, FRONTLINE reporter Najibullah Quraishi goes on a dangerous journey inside both Taliban- and ISIS-held territory and exposes the harsh reality that not only is the Taliban once again wielding power, but the threat from ISIS looms large.

The Luanda Leaks: As part of a worldwide investigation with the International Consortium of Investigative Journalists that draws on a trove of more than 700,000 leaked documents, FRONTLINE reporter Richard Bilton examines how Africa's richest woman, Isabel dos Santos, built a business empire with access to state funds from Angola, one of the poorest countries on earth — and the role U.S. companies have played in helping her amass her fortune.