Donald Rumsfeld sits for extended interviews with director Errol Morris, working through the thousands of internal memos he dictated during his years in Washington, the ones he called 'snowflakes.' Rumsfeld reads his own words back on camera, from his early days as a Nixon aide through two stints as Secretary of Defense, the second spent building the case for and then running the Iraq War. Morris keeps returning to the film's title, drawn from Rumsfeld's famous distinction between known knowns, known unknowns, and unknown unknowns, pressing him on what he actually meant and whether the phrase excused decisions made on thin evidence. Archival footage of press briefings and cabinet meetings sits alongside the present-day interview, letting viewers watch Rumsfeld construct and defend his own record in real time. Morris asks pointed questions about Abu Ghraib, WMD intelligence, and the run-up to war; Rumsfeld answers with the same practiced fluency he used at the Pentagon podium, smiling through most of it.