Each winter, Montana livestock officials who say they are protecting cattle from the disease brucellosis kill bison that migrate out of Yellowstone National Park. But this killing of members of America's last wild buffalo herd has led to clashes among Native Americans, ranchers, and radical environmentalists. This documentary examines the controversial killing by weaving together the stories of a 500-mile Native American march for the buffalo, the travails of a family trying to keep its cattle ranch, and the daring tactics of a band of environmental activists.