Writer-producer-director Stanley Nelson had trod the civil-rights path before for American Experience, and, as producer, emerged with thoughtful, informative yet undeniably and understandably emotional documentaries on, among others, Emmitt Till, Jesse Owens, and the 2011 study Freedom Riders, of which this new two-hour American Experience is a sociological sequel. It covers the 10-week period in 1964 in which student volunteers, carefully chosen and emotionally vetted, were sent to the toxically segregated state of Mississippi with the intent of using nonviolent forms of protest to urge reforms. At the start of that summer, three volunteers went missing. At the end of the summer, their bodies were found. In between was a riveting, high-stakes battle between what was and what ought to be. Fifty years later, the action presented here remains riveting to watch. Riveting, and often horrifying – but also, when looking at those dedicated youngsters, inspiring. Check local listings.