It is more than apparent that Jess Franco conceived The Demons not long after Ken Russells The Devils (1971) came out. The Devils was a sensationalistic take on the witchfinder theme that gained prominence a few years earlier with the success of Michael Reeves Matthew Hopkins Witchfinder General (1968). The Devils concerned a true 17th Century incident where the Catholic Church determined to punish what it believed was an outbreak of possession at a convent in France. Russells frequently blasphemous depiction of the sexual hysteria caused a sensation and had the film banned in some areas. The similarity between the two films seems obvious in the choice of titles The Devils/The Demons. Only, where Ken Russell was depicting a true historical incident and letting loose with typically schoolboyish outrages, Jess Franco does no more than create another of his works of softcore erotica. Franco is probably the only director who could take a story about nuns being tortured and witches burned at the stake and turn it into a work of erotica.
There is also something hypocritical about Francos take on things. His indifference to the moral issues that drive The Devils is surely indicated in that he cannot ever seem to decide if the two sisters here are persecuted innocents or are actual witches being seduced by The Devil and others into enacting their mothers vengeance against her persecutors the film has them as both depending on whatever suits a particular scene. Not to mention that the evidence he offers of possession is on the dubious side at the start, the determination of Anne Liberts possession is based solely on one of the other nuns seeing her masturbating.
Plots were never a strong suit for Franco. After starting off with the persecution of the two sisters by witchfinders, the film trails off once the two sisters leave the convent. Here there is never much more than a sense of things happening as they pass from one encounter to the next where crucially there is no real momentum to the plot. The latter half of the film peters off into nothing terribly interesting happening.
The Demons has been seen in a variety of cut versions. The full original restored version runs to 103 minutes, although this has been cut of anything up to twenty minutes in the US release and other versions. One of the oddities of the film is that Franco has made it as a sequel of sorts to his earlier The Bloody Judge/Night of the Blood Monster (1970) and features a continuation of the historical character of the tyrant Judge George Jeffreys who was played by Christopher Lee in the earlier film. John Foster (a pseudonym for French actor Cihangir Gaffari) takes up the role here. Clearly, continuity is not a big issue for Franco as both films feature two entirely different deaths for Jeffreys.
Jess Francos other genre films are: The Awful Dr Orloff (1962), The Sadistic Baron Von Klaus (1962), The Secret of Dr Orloff (1964), Attack of the Robots (1966), The Diabolical Dr Z/Miss Death (1966), The Blood of Fu Manchu (1968), Necronomicon/Succubus (1968), The Castle of Fu Manchu (1969), Justine (1969), Kiss Me Monster (1969), 99 Women (1969), Sadisterotica/Red Lips (1969), The Girl from Rio (1969), Venus in Furs/Paroxysmus (1969), The Bloody Judge/Night of the Blood Monster (1970), Count Dracula (1970), Eugenie/Philosophy in the Boudoir (1970), Nightmares Come at Night (1970), Vampyros Lesbos (1970), Dracula, Prisoner of Frankenstein (1971), She Killed in Ecstasy (1971), The Corpse Packs His Bags (1972), Daughter of Dracula (1972), Doctor Mabuse (1972), The Erotic Adventures of Frankenstein (1972), The Silence of the Tomb (1972), The Sinister Eyes of Dr Orloff (1973), The Bare-Breasted Countess/Eroti-Kill/Female Vampire (1973), The Erotic Adventures of Maciste in Atlantis (1973), The Obscene Mirror (1973), A Virgin Among the Living Dead/Christina, Princess of Eroticism (1973), Lorna the Exorcist (1974), The Perverse Countess (1974), Eugenie (1975), Doriana Grey (1976), Jack the Ripper (1976), Night of the Assassins (1976), Sexy Sisters (1976), Greta the Mad Butcher/Wanda the Wicked Warden (1977), Call of the Blonde Goddess/Voodoo Passion (1977), Wicked Women (1977), Demoniac/Exorcism/The Ripper of Notre Dame (1979), Man Hunter/The Devil Hunter (1980), White Cannibal Queen (1980), Bloody Moon (1981), Oasis of the Zombies (1981), Revenge of the House of Usher (1982), Grave of the Living Dead (1983), The Treasure of the White Goddess (1983), The Sinister Dr Orloff (1984), Mansion of the Living Dead (1985), Faceless (1987), The Killer Barbies (1996), Lust for Frankenstein (1998), Marie-Cookie and the Killer Tarantula in 8 Legs to Love You (1998), Tender Flesh (1998), Vampire Blues (1999), Vampire Junction (2001), Incubus (2002), Killer Barbies vs Dracula (2002), Snakewoman (2005), Paula-Paula (2010), Al Pereira vs the Alligator Ladies (2012), Crypt of the Condemned (2012) and Revenge of the Alligator Ladies (2013).