Director Rory Kennedy goes back in time to recapture a particularly painful moment in the history of American failure, the chaos that followed withdrawal of U.S. troops from Vietnam. The movie tells us it was assumed that the North Vietnamese, fearful of a devastating Nixon response, would not invade the South. Watergate took care of that fear, and the North began marching toward Saigon. As the North Vietnamese approached Saigon, South Vietnam went into full panic mode: Many of those who had aided the American war effort sought an escape route. Kennedy (Ethel and Ghosts of Abu Ghraib) masterfully combines newsreel footage and interviews to tell a story full of pain and betrayal. We meet Americans who worked hard to help their Vietnamese associates, many of whom had become friends. Some of these Americans took matters into their own hands, throwing policy aside to do what they thought was morally right. Some of the stories are chastening: Having lost a son in combat in Vietnam, U.S. Ambassador Graham Martin couldn't bring himself to admit that Vietnam had become a lost cause. Kennedy chronicles the last day of evacuations with sequences that are as tense as any you'll find in most thrillers. Kennedy remains true to her story: She never suggests that what happened in Vietnam in any way corresponds to any current situation in which the U.S. finds itself, but it's difficult not to wonder about the fates of Iraq and Afghanistan as you watch this revealing documentary.