“It’s supposed to be about homosexuals, and you don’t even see the boys kiss each other,” Jean Renoir once said of Rope. “What’s that?” This comment, seemingly dismissive, actually reaches to the heart of the movie, a work very much about what we see, and what we don’t. A virtuosic formal achievement, Rope plays out as a single continuous shot, accomplished by the use of hidden cuts. Hitchcock’s first color film was adapted by gay screenwriter Arthur Laurents from a stage play that was, in turn, based on the infamous 1924 Leopold and Loeb case, in which two young lovers murdered a 14-year-old boy in cold blood. Yet the on-screen depiction of homosexuality was verboten in the 1940s, so Farley Granger and John Dall, the queer actors cast as the killers, gamely maneuvered through a scenario that, even by the standards of a Hitchcock film, is drenched in innuendo.