I can't honestly call this film "good" in the conventional sense. The directing is terrible, with very poor pacing and every "shock" telegraphed far too long in advance, Gayle Hunnicutt is a waste of space apart from a couple of scenes where she gets to go nuts (when there are only four significant characters who aren't invisible ghosts, it's just plain careless to seriously underuse one of them), and Roddy McDowall manages to give a masterclass in overacting in a movie where nothing and no-one is exactly understated.
But hey, it's a lot of fun! Basically, it's "The Haunting" with all the subtlety replaced by things which might appeal to people who had just seen a ground-breaking new movie called "The Exorcist", though without having the courage to go anywhere near that far. Still, we do get sex-crazed ghosts, an abundance of spiky objects flinging themselves at our heroes, possibly the most extended scene ever in which the ultimate manifestation of satanic evil is represented by repeatedly throwing an understandably annoyed cat at some long-suffering actress, completely bonkers "science", and undoubtedly the silliest method of defeating a seemingly omnipotent supernatural force in the entire history of cinematic ghost-busting.
Pamela Franklin as the Linda Blair substitute comes out of it with the most credit, but Clive Revill (whoever he was) plays a character so unlikable that when, quite early in the film, the poltergeist attacks him with just about everything in the room that could possibly inflict damage, you'll definitely be rooting for the ghost (unfortunately its aim is lousy). And Michael Gough has such an unrewarding rôle that he probably had more fun that time he had to flounce about in pink satin as the king of the Moon. Still, second-rate though it is, it's certainly not dull. And Roddy McDowall heroically trying to render his lines audible while leaning into the blast of a wind machine turned up to 11 is a sight to behold!
Eerie ghost story adapted by regular Twilight Zone writer Richard Matheson from his own novel. Presumably he had read Shirley Jackson's The Haunting of Hill House because the set up is similar, as well as the title. A team of experts in the paranormal are hired to spend a week in a cursed castle and produce definitive proof of malign possession.
The key personnel is Pamela Franklyn as a jittery medium and Clive Revill as the rationalist who proposes to throw science at the problem. It is immediately clear that this isn't all happening in someone's head. Eventually the boffin wheels out his supercomputer with which he intends to rid the house of its degenerate demon.
The premise has lost some freshness in recent years, as there has been a glut of ghost stories. What distinguishes this one is the really unsettling photography and set design which gives the film the feeling of a nightmare. There's a spooky score of electronic atmospherics. And the effects are state of the art for the period.
There's a sensational moment when Franklyn's body starts to produce ectoplasm! The final explanation isn't a strength, but the late appearance of Michael Gough as the mummified body of an evil Edwardian gentleman is quite disturbing. There is a touch of the grotesque to the horror. It's not as stylish as The Haunting, but it's much more macabre.