“Petro”begins in September 2021 at the launch event of Gustavo Petro’s presidential campaign. This former M-19 (April 19 Movement) guerrilla leader suddenly becomes the front runner. With unprecedented access to Petro, Mattison’s documentary follows the highs and lows of the Colombian progressive movement and Petro’s historic campaign for president through Election Day. The documentary also looks back at the violent history of Colombia’s guerrilla warfare, from attacks by both M-19 and the FARC to President Álvaro Uribe’s brutal response which ended in the execution of hundreds of civilians wrongly accused of being guerrilla sympathizers.