In July 1962, Harold Macmillan sacked a third of his Cabinet, including Chancellor of the Exchequer and some of his oldest political friends. Did the normally unflappable Macmillan panic? Was there, as Macmillan claimed, a plot to overthrow him and, if so, who was behind it? Rare archive film and interviews with Macmillan's closest confidants and victims of his purge offer new evidence for this unprecedented act of political butchery.