Adapted from Truman Capote’s celebrated nonfiction novel, this grim drama stars Robert Blake and Scott Wilson as real-life murderers Perry Smith and Dick Hickock and John Forsythe as investigator Alvin Dewey. Shot in black-and-white and told in a kind of cinéma vérité style, the story concerns the ruthless murder of the Clutter family, the manhunt that follows, and the trial…