Known by many different titles, among them "A Bay of Blood", "Carnage", "Twitch of the Death Nerve", and "Last House on the Left, Part II", this marvelously gory predecessor to slasher movies is a fine exercise in style by Italian master Mario Bava.<br /><br />A prime piece of bayside real estate is being coveted by some ruthless and sadistic individuals; one body after another drops, hence the title "Reazione a catena", translated as "chain reaction" in English. In addition to our major players, anyone else foolish enough to drop by (including a quartet of playful youngsters) is fair game. The film is packed with some memorably graphic mayhem; the sickle to the face will always be my personal favorite, although there's also a nifty decapitation, and a show-stopping, prime example of coitus interruptus that was ripped off later in "Friday the 13th, Part 2". Carlo Rambaldi, later a creator of creature effects in such films as "King Kong" (1976), "Alien", "E.T. the Extra-Terrestrial" and "Cat's Eye" is the man behind the gore here, and his work is outstanding.<br /><br />What will give this film the edge over the many North American imitators that it inspired is the elegance and flair that Bava (also serving as his own cinematographer here, and doing an excellent job) brings to the proceedings. The film is beautiful to look at; the setting is wonderful. I'll also find hard to forget the striking image of an octopus slithering over the face of one of the many victims. The film is also enhanced by the lovely music of Stelvio Cipriani, which at times involves lots of percussion and becomes heavily atmospheric.<br /><br />This film gets right down to business pretty quickly; in short order two of the characters get knocked off although the first nine or so minutes, rather effectively, play out without dialog.<br /><br />This is a genuinely great film that deserves a certain amount of respect, both for its entertainment value and its influence. I highly recommend it.<br /><br />9/10