Sam Green and Bill Siegel's documentary about a radical group whose stated goal was the violent overthrow of the U.S. government details a valuable chapter in the history of the '60s protest movement and leftism in America. The Weathermen were a faction of Students for a Democratic Society (SDS), one of the driving forces behind the period's mass protests against social injustice and the Vietnam War. Frustrated by SDS's adherence to non-violent dissent, the Weathermen broke off and adopted a more combative approach. As the student protests ebbed in the 1970s, the group went underground and shifted tactics, embarking on a terrorist campaign against the U.S. government. For years, the Weather Underground evaded the authorities' grasp, even as it pulled off high-profile bombings against government targets. Their momentum petered out in the 1980s, as one by one the organization's members surrendered after years on the run. The Weather Underground uses extensive archival footage and revealing interviews with the surviving members to trace the group's evolution and place their actions in the context of the period's tumultuous events.