In the Zapruder film, a man stands under an open black umbrella on a clear day, seconds before Kennedy is shot in Dealey Plaza. Errol Morris uses that single strange detail to interview Josiah Thompson, a longtime assassination researcher, about how one visual anomaly can spawn decades of conspiracy theory. Thompson walks through the reasoning that turned the umbrella into a signal device, a coded message to the shooters, before Morris reveals what actually happened when the man, Louie Steven Witt, came forward years later and explained himself: the umbrella was a silent protest referencing Joseph Kennedy's prewar dealings with Nazi Germany, an old political dig aimed at the president's father that had nothing to do with an assassination plot. Morris uses the episode to make a broader point about evidence and coincidence, how even the most bizarre-looking detail can have a mundane explanation, and how the absence of an explanation is what really fuels conspiracy thinking. It runs about five minutes and lands its argument in that space.