At the beginning of the movie a pharmacist receives an anonymous letter that threatens him of death. And the murder actually happens. Seems very simple but nothing is what it seems and the journey to the truth will be long and difficult. The book is excellent and the movie is at par with it and very faithful to the romance. Great direction. Incredible cast with Gabriele Ferzetti in his best interpretation together with the one in "C'era una volta il West" and Gianmaria Volonté simply beyond reach as always. Many other great actors. Yes I am an enthusiast 'cause there's not a word or a shot out of place in this movie and the plot is ingenious. Who is going to see this film for the first time will be taken away by the developments (the pace seems to be calm but looking in between the kinks you may realize that many things are going rapidly on). Trying to figure out what is the kernel of the happenings and the "reasons" for the murder is a very interesting exercise but it's highly unlikely for the spectator not to experience a big surprise at the end. In my opinion Elio Petri at his best (I mean at the same level of his other masterwork: La classe operaia va in Paradiso)