Matt Mochary and Jeff Zimbalist's documentary traces the history of Grupo Afro-Reggae, a community-based action group that arose in Vigario Geral, one of the notorious favelas — slums — that ring Rio de Janeiro. Brazil's crowded, crime-ridden shantytowns lack the most basic social and municipal services, and are notorious breeding grounds for violence and despair run by brutally viciously competitive drug gangs. In August 1993, a drug gang ambushed a police car carrying four officers, including one who was notorious for shaking down Vigario Geral residents, and killed them all; in retaliation, a special military police unit made a raid that killed 21 locals, none involved in the ambush. Andersen Sa, a low-level foot soldier for the Red Command cartel that ran Vigario Geral had already seen most of his childhood friends die or disappear into Brazil's notoriously brutal prison system, but losing his brother in the raid galvanized him to change direction. Sa stopped working for the Red Command and joined forces with a neighbor, Jose Junior, who had already put his faith in what he called the "Shiva effect," named after the dualistic Hindu god of destruction and rebirth. Junior and Sa believed music could be more than entertainment — it could be a force for social change. Their Grupo AfroReggae, whose musical influences ranged from rap and hip-hop to bossa nova, rock and Cajun music, gave free performances, while the larger organization established a community center and offered programs that taught drumming, dance, capoeira and music to local youths. The organization made a samizdat film exposing police brutality in the favelas, while also mediating between drug gangs and offering constructive role models in an environment where drug dealers easily earn 25 times the salary of the average dark-skinned Brazilian adult. To date, AfroReggae is established in nine favelas, including the notorious Cidade de Deus, and while it can't mitigate the overarching effects of economic deprivation and systematic exclusion from the cultural mainstream, its positive influence is evident. Zimbalist and Mochary focus on the charismatic Sa, whose articulateness and dramatic personal history make him a natural face for the organization — his near-miraculous extraordinary recovery from a surfing accident that could have paralyzed him for life is the stuff of personality cults. But the larger message remains clear: Unified communities have more power than they realize, and the most vicious enemy of progress is learned helplessness.