Claude Marchand (Jean-Pierre Aumont) is a journalist who jets into France from an overseas assignment only to be told as he arrives that he has a message which says he is not stopping, since his boss has ordered him to go straight to Spain for another report. He is sanguine about this, accepting it as part of his job, and anyway it's not as if the region he is heading for isn't picturesque, it's a village by the sea so there will be sun, sand and sangria on offer as he seeks out the world famous - and blind - sculptor Franz Badalescu (Boris Karloff). The artist lives in a large villa with his wife Tania (Viveca Lindfors), a loyal partner to him who has ensured his work has gotten out to the aesthetes, but what it there was something a tad... off about it?
Boris Karloff's final few films tended to be lumped into one indigestible mush by horror fans, most obviously those last four Mexican ones released largely after his death that featured minimal participation for him as he was only taking the job because he was dying by that point and, not wishing to ever retire, was determined to keep working right to the end, also providing for his family in the process. But unlike some stars most associated with the horror genre, some of those final roles were actually in very decent movies, with Peter Bogdanovich's Targets filmed in Karloff's last year and one of his greatest performances, not to mention his part in making Michael Reeves' The Sorcerers as good as it was.
So where did that leave Cauldron of Blood, an oft-derided shocker shot in Spain at the then-newly discovered by tourists Torremolinos resort? For many of those curious enough to seek it out, they would tell you it was better left alone, a footnote to a stellar career from one of the stars who made horror almost respectable given his well-known reputation for being an absolute gentleman in all his dealings. But for those completists who appreciated Karloff for precisely those debts they owed him to their favourite style of entertainment, it was irresistable mainly because it was late sixties, early seventies horror such as this which marked the change from the spooky and atmospheric to the more lurid and, dare we say it, gory dominating for decades to come.
Of course, the spooky method of chiller making never went away and returned with a vengeance once the so-called torture porn fad briefly sparked and fizzled, which makes Cauldron of Blood something of a relic anyway. Not that was an absolute bloodbath, but it did have a degree of the stronger stuff of giallo about it, even as it replicated the essential plot point of House of Wax for its chief source of shocks, though it perhaps had more in common with Roger Corman's A Bucket of Blood, with Karloff an unlikely Dick Miller. You guessed it - what's up with those sculptures is that there are real skeletons inside them, culled from the locals at the village (there are never any police around, so presumably nobody thought to contact them), yet Badalescu, being blind, thinks he is using basic armatures to model the clay over.
Which left the villain of the piece as Tania, she is frankly bonkers thanks to a trauma in her past which haunts her nightmares, as we see in a very strange montage sequence of supposedly terrifying imagery - her husband's face rotting to the skull, herself as a frightened little girl being whipped by her adult self dressed in an SS uniform - and therefore marks her out as instrumental in the murders, the cauldron of the title being an acid bath. Meanwhile Claude investigates, or that was the idea, but actually he spends most of the time having a rare old holiday, hanging out with dolly birds including proto-Pia Zadora-alike Rosenda Monteros and proto-Rebecca de Mornay-alike Dyanik Zurakowska who naturally (or unnaturally) end up menaced when Boris needs to craft his latest masterpiece. Although it has its moments, it's never quite as incoherent as it threatens to be with its patently piecemeal assembly (it was released three years after it was filmed), and though Karloff was elderly he couldn't avoid bringing a touch of class, even sympathy, to the cheap and semi-cheerful movie. Music by Ray Ellis.