Husband and wife grave-robbers Augusto (Fernando Sánchez Polack) and Flora (Montserrat Julio) are raiding a rich girl's tomb, when a mysterious masked maniac casts a voodoo spell that raises Gloria Irving (Norma Kastel) from the dead. Zombie-Gloria swiftly splatters them both, then races across the graveyard, her diaphanous gown flowing along the midnight breeze in eerie slow-motion. Meanwhile in Swinging London, Gloria's sister Elvira (Romy) and playboy psychologist Lawrence Redgrave (Vic Winner) consult with seemingly benevolent Indian mystic Krishna (Paul Naschy), hoping to uncover the truth behind an outbreak of zombie sightings and ritual murders around town.
Elvira enters into a sexual liaison with Krishna at his country manor, formerly home to the notorious devil-worshippers the Whatley family, much to the annoyance of his acolyte/lover Kala (Mirta Miller). But quicker than you can say Rosemary's Baby (1968), Elvira is plagued by wide-angle nightmares about wild satanic orgies with sacrificial killings, gold painted ladies and hairy blue witches presided over by a green-skinned Satan (Paul Naschy, again). As the killings continue, clueless cops send occult expert Lawrence to visit Krishna's estate, where he begins an affair with sexy maid Elsie (Maria Kosty). He uncovers a connection wherein the victims all came from families once settled in India, now pawns in a black magic war between Krishna and his hideously disfigured twin brother, Kantaka (Paul Naschy - third time's the charm!).
Another collaboration between Argentinean-born director Leon Klimovsky and Spanish horror icon/screenwriter Paul Naschy (real name: Jacinto Molina Alvarez), Vengeance of the Zombies is stylishly shot and has an agreeably off-kilter atmosphere to enhance its loopy plot. Sporting some fabulous early Seventies decor and one seriously groovy score by Juan Carlos Calderon, there is a delicious The Avengers meets Scooby-Doo by way of EC comics vibe at work here that compensates for the occasionally incoherent storytelling. The film unfolds with several disparate plots slowly converging into one, throwing in giallo-style murders, plentiful naked ladies, satirical attacks on then-trendy Indian mysticism, and good old fashioned gothic horror, before a head-scratching shock twist unveils a hitherto peripheral character as a major player.
Some critics have drawn parallels with British groovy gothics such as Curse of the Crimson Altar (1968) and Dracula A.D. 1972, which equally influenced Klimovsky and Naschy's earlier Dr. Jekyll versus the Werewolf (1972). Naschy's love of classic horror motifs is to the fore in the romantic overtones and a plot that hinges on a tortured anti-hero torn between evil forces and the woman he loves. He packs his script with references to Senegalese voodoo, Baron Samadhi (see also: Live and Let Die (1973)), English rural witchcraft, and cod-Eastern philosophy ("Life is a lie complete with glorious colours. Free yourselves, because nirvana approaches soon!"), that results in somewhat of a mishmash, but a sincere and articulate one. Naschy the writer also ensures that Naschy the actor gets plenty of action between the sheets as sexy Kala and Elvira throw themselves at him, although Krishna ultimately stands as weaker beside his diabolical twin, suggesting this is partly a satirical attack on guru figures like the Maharishi.