Widely considered Bava's most violent film, its emphasis on graphically bloody murder set pieces was hugely influential on the slasher film subgenre that would follow a decade later. In 2005, the magazine Total Film named A Bay of Blood one of the 50-greatest horror films of all time.
At night in her bayside mansion, wheelchair-bound Countess Federica (Isa Miranda) is attacked and strangled to death by her husband Filippo Donati (Giovanni Nuvoletti). Moments later, Filippo himself is attacked and brutally stabbed to death by an assailant, and his corpse is then dragged to the bay. Upon investigation, the police find what they believe to be a suicide note written by the Countess, but Donati's murder goes undiscovered.
Real estate agent Frank Ventura (Chris Avram) and his lover Laura (Anna Maria Rosati) are plotting to take possession of the bay. After the Countess refuses to sell her home and property to them, the couple hatch a scheme with Donati to murder his wife. To finalize their plan, Ventura needs Donati's signature on a set of legal documents. They have no idea, however, that Donati himself has been killed.
Their curiosity piqued by news of the murder, four local teenagers break into the seemingly deserted mansion. Shy teen Bobby (Robert Bonnani) stays behind in the house while his date Brunhilda (Brigitte Skay) skinny-dips in the bay. She has barely begun her swim when Donati's rotting corpse rises from the water and collides with the nude girl. Terrified, Brunhilda rushes out of the water towards the mansion only before the unseen assailant catches up and murders her with a billhook. After Bobby is killed with the billhook slammed into his face, the killer takes a spear and impales Duke (Guido Boccaccini) and his girlfriend Denise (Paola Rubens) while they have sex.
It transpires that the Countess's illegitimate son Simon (Claudio Volonté) is the killer. After killing Filippo Donati, he is now conspiring with Frank Ventura, who offers Simon a large cash pay-off in exchange for agreeing to sign the relevant legal documents turning sole ownership of the Countess's estate and property over to Ventura. Their scheme is dealt a potentially ruinous blow when Countess Federica's estranged daughter Renata (Claudine Auger) unexpectedly appears, determined to ensure that her mother's estate comes into her possession. A search for the Countess's will proves unsuccessful, and Ventura, who believes that Renata may be the rightful beneficiary, urges Simon to finish his half-sister off.
Accompanied by her husband Albert (Luigi Pistilli), Renata visits the house of Paolo Fassati (Leopoldo Trieste), an entomologist who lives on the grounds of Donati's estate. Fassati's wife Anna (Laura Betti) tells them that Donati was responsible for the Countess's death, and says that Simon will probably end up with the property. Renata, who had no idea she had a half-brother, swiftly dispenses with any notion of sibling affection and immediately begins making plans with her husband to murder Simon, who at the same time is orchestrating Renata's demise.
After discovering Donati's mangled and rotting corpse on Simon's boat, Renata and Albert head to Ventura's house. Upon their arrival, Ventura launches a brutal attack on Renata, determined to kill her, but Renata gains the upper hand and stabs Ventura with a butterfly knife. Paolo Fassati, who witnesses the assault, attempts to telephone the police but is confronted by Albert, who strangles him to death. To ensure there are no additional witnesses, Renata decapitates Anna with an axe.
Ventura's partner Laura arrives, planning to meet up with him. When Simon discovers that it was the pair who had plotted with Donati to kill his mother, he slowly strangles Laura to death. No sooner has he exacted his revenge than Simon himself is murdered by Albert. The wounded Frank suddenly reappears, but Albert succeeds in killing him after a brief struggle.
Secure in the knowledge that there are now no other living heirs, Albert and Renata return home to await the announcement of their murderously guaranteed inheritance. They are met at the front door by their own two children, who have found their parents' double-barreled shotgun and want to play. Before either mother or father can react, the children shoot their parents to death. Thinking that mom and dad are playing dead, the young boy and girl rush off outside to find another game.Claudine Auger - Renata Donati
Luigi Pistilli - Albert
Claudio Camaso - Simon (credited as Claudio Volonté)
Laura Betti - Anna Fossati
Leopoldo Trieste - Paolo Fossati
Isa Miranda - Countessa Federica Donati
Chris Avram - Frank Ventura
Anna Maria Rosati - Laura (credited as Anna M. Rosati)
Brigitte Skay - Brunhilda (Hilda)
Paola Montenero - Denise (credited as Paola Rubens)
Guido Boccaccini - Duke
Roberto Bonanni - Robert (Bobby)
Giovanni Nuvoletti - Filippo Donati
Renato Cestiè - Son (uncredited)
Nicoletta Elmi - Daughter (uncredited)
The genesis of A Bay of Blood was a simple story idea concocted by Bava and actress Laura Betti as a way to allow them to work together again, as the two had got along so well on Bava's Hatchet for the Honeymoon (1969). The project's original title was Odore di carne ("stench of flesh"), and the murder-filled story had enough promise to convince producer Giuseppe Zaccariello to provide financial backing. Numerous other writers, including Zaccariello himself, had their hands involved in devising the final screenplay.
The film began production in early 1971, originally under the shooting title Cosi imparano a fare i cattivi ("thus do we live to be evil"), which was soon changed to Reazione a catena ("chain reaction"). Bava showed great enthusiasm for the film, but unfortunately the movie's budget was extremely low, and it had to be shot very quickly and cheaply. Due to the severe budgetary restrictions, Bava not only acted as his own cinematographer, but also utilized a simple child's wagon for the film's many tracking shots.
The location shooting was mostly completed at Zaccariello's Sabaudia beach house and its outlying property. Bava had to resort to various camera tricks to convince the audience that an entire forest existed when in fact, only a few scattered trees were at the location. Betti recalled, "All of this had to occur in a forest. But where was it? Bava said, 'Don't worry. I will do the forest.' And he found a florist who was selling these little stupid branches with little bits of foliage on them, and he began to make them dance in front of the camera! We had to act the scenes strictly in front of those branches—if we moved even an inch either way, the 'woods' would disappear!"
To ensure the utmost realism in depicting the thirteen different murders, Carlo Rambaldi was hired to provide the gruesomely effective special make-up effects. The 1971 Avoriaz Film Festival jurors awarded the film the Best Make-Up and Special Effects Award. Rambaldi's effects work also earned the film a "Special Mention" Award at the prestigious Sitges Festival in 1971.
When the film was picked up for U.S. distribution by exploitation specialists Hallmark Releasing Corporation, they titled the film Carnage and copied their own successful advertising campaign for Mark of the Devil by proclaiming that Bava's film was "The Second Film Rated 'V' for Violence!" (Devil having been the first). The movie was apparently unsuccessful, and it was withdrawn and re-released in 1972 under the now common title Twitch of the Death Nerve. It reportedly played for years under this title in drive-ins and grindhouses throughout the country.
As the latest offering from a noted genre specialist, A Bay of Blood was greeted with disappointment and disgust by several critics, especially by those who were fans of the director's earlier, more restrained films. At the 1971 Avoriaz Film Festival, where the movie had its world premiere, Christopher Lee attended a screening of the film, having expressed an interest in seeing the latest effort from the director of The Whip and the Body, which Lee had starred in eight years before. Lee was reportedly completely revolted by the movie.
It remains Bava’s most controversial film and maintains a mixed critical reception. Jeffrey Frentzen, reviewing the film for Cinefantastique, called Twitch of the Death Nerve "the director's most complete failure to date. If you were appalled by the gore and slaughter in Blood and Black Lace, this latest film contains twice the murders, each one accomplished with an obnoxious detail... Red herrings are ever-present, and serve as the only interest keeping the plot in motion, but nothing really redeems the dumb storyline." Gary Johnson, on his Images website, said that "Twitch of the Death Nerve is made for people who derive pleasure from seeing other people killed...The resulting movie is guaranteed to make audiences squirm, but the violence is near pornographic. In the same way that pornographic movies reduce human interactions to the workings of genitals, Twitch of the Death Nerve reduces cinematic thrills to little more than knives slicing through flesh." Phil Hardy's The Aurum Film Encyclopedia: Horror, while noting that Bava was able to "achieve some striking images", opined "Zooms, no doubt programmed by the imperative to work quickly, spoil some scenes that cried out for Bava's particularly fluid use of camera movement which were so much in evidence in Operazione Paura (1966)."
Joe Dante, on the other hand, was enthusiastic about the film, writing in The Film Bulletin (later reprinted in Video Watchdog) that it "features enough violence and grue to satisfy the most rabid mayhem fans and benefits from the inimitably stylish direction of horror specialist Mario Bava (Black Sunday). Assembled with a striking visual assurance that never ceases to amuse, this is typical Bava material, simply one ghastly murder after another---13 in all---surrounded by what must be one of the most preposterous and confusing plots ever put on film." In Fangoria, Tim Lucas wrote thirteen years after the film's theatrical release that "Twitch unreels like a macabre, ironic joke, a movie built like an inescapable trap for its own anti-hero...Seen today, the violence in this movie remains as potent and explicit as anything glimpsed in contemporary "splatter" features..."
The film has a favorability rating of 80% on the Rotten Tomatoes movie review website, out of ten internet reviewers surveyed.
Several critics have noted that the film is probably the most influential of Bava's career, as it had a huge and profound impact on the slasher film genre. Writing in 2000, Tim Lucas wrote that Bava's film is "the acknowledged smoking gun behind the 'body count' movie phenomenon of the 1980s, which continues to dominate the horror genre two decades later with such films as Scream, I Know What You Did Last Summer and their respective sequels." According to Gary Johnson, "Twitch of the Death Nerve is one of the most imitated movies of the past 30 years. It helped kick start the slasher genre… [Bava’s] influence still resonates today (although somewhat dully) in movies such as I Know What You Did Last Summer, Scream and Urban Legend."
While most slasher movies owe a considerable debt to Bay's somewhat nonsensical narrative and its emphasis on bodily mutilation, at least one film was directly imitative: Friday the 13th Part 2 notoriously copied two of Bava's murder sequences almost shot for shot: one character is slammed in the face with a panga machete (even though Bava's film had a billhook and not a machete), and two teenage lovers are interrupted when a spear impales both of them. Along with The Burning, Just Before Dawn (1981) and several other similarly-plotted slashers, Friday specifically "followed Bava's inspired cue, having young people stalked by violent death amid beautiful wooded settings."
According to Tim Lucas, the film is "probably known by more titles than any other movie ever released" Its best-known title is Twitch of the Death Nerve, but it has been shown theatrically and appeared on home video under a bewildering variety of titles. In Italy, the pre-production draft screenplay was called Odore di carne ("The Odor of Flesh"), but the shooting title was originally Cosi imparano a fare i cattivi ("Thus do we live to be evil"). After production was completed, it was announced as Antefatto ("Before the Fact"), but when finally released to theatres, the title had changed, this time to Ecologia del delitto ("The Ecology of Crime"). When the film did poorly on its initial release, it was pulled from Italian theaters and retitled Reazione a Catena ("Chain Reaction"), and was later re-released as "Bahia di Sangre" ("Bay of Blood").
In the United States, it was originally to be released as Carnage, but then retitled Twitch of the Death Nerve. It is also known as simply Bay of Blood, Last House on the Left – Part II (or Last House – Part II) and New House on the Left.