Just watched the movie. It’s about a paranoid surveillance experts played by Gene Hackman and John Cazale (RIP to both) managing to record a mysterious conversation between a couple. Not horror (it’s a neo-noir mystery thriller) but it does have scary elements with its themes of paranoia and the fear of being watched, especially the moment Gene Hackman’s character enters the hotel room of the couple and flushed the toilet then blood came out clogging it; it honestly feels straight out of horror. Plus the music by David Shire just perfectly amps up the atmosphere of the entire movie.