For years, the Earth Liberation Front--autonomous individuals operating in separate anonymous cells without any central leadership--carried out spectacular direct-actions against businesses that destroy the environment. Some of the targets were logging corporations, SUV dealerships, ranger stations, a slaughterhouse and a multi-million dollar ski-lodge at Vail, Colorado that was expanding into national forest. As authorities were not able to crack the case and disbanded many years later, the FBI got lucky when they were led to a former activist who agreed to co-operate with them and become an informant. If A Tree Falls provokes hard questions about environmentalism, activism, and the way 'terrorism' is defined by following the story of the activists who were turned over to the FBI, and their fate...