Argento chased The Bird with the Crystal Plumage’s box-office success with his most accessible giallo thriller, a hybrid mystery/buddy movie that pairs Karl Malden’s blind cruciverbalist with James Franciscus’s intrigued reporter. Here Argento experiments with his chosen genre’s procedural-style fetishism: the movie’s title refers to the number of leads that will ultimately steer the amateur sleuths to a mysterious serial killer. Argento constructs the film’s mystery within the framework of a crossword puzzle whose clues slyly allude to seeing, sightlessness, and how the limits of our perception obscure the truth. The movie’s eruptive and still-shocking violence fosters a nightmarish tension throughout, and perfectly complements Ennio Morricone’s alternately slinky and discordant avant-jazz score. 4K digital restoration by Cinecittà.