Police Sergeant Howie (Edward Woodward) travels to the remote Hebridean island Summerisle following an anonymous report of a missing girl.
On arrival the locals claim never to have seen or heard of her. Howie is repelled by their bawdy songs and 'sinful' behaviour: he is a devout Christian.
Slowly the story changes as he investigates and Howie finds out the island has embraced an ancient pagan religion.
No good will come of this.
CW: Nudity, animal and human sacrifice, awful folk music
While this can't quite claim to have invented folk horror it essentially put it on the map.
By modern standards it's so mild as to almost be consigned to billing as a conventional drama, but the themes and final scene make it definitely horror.
Faced with indifference from the locals Howie acts in classic 70s bull in a china shop copper fashion going round confronting people, accusing them of stuff and threatening to arrest them for whatever thing he currently seems offended by. This includes teaching paganism in the school and so on.
Christopher Lee is good fun as the absurdly matter of fact Lord Summerisle, whether that's in tweed or a dress and long wig. Britt Ekland is badly dubbed as the 'lusty publican's daughter'.
This it to horror what Planet of the Apes is to sci-fi. Filled with iconic visuals that people know even if they've never seen it.
There's a subtlety to its 70s directness that is an asset when the reveal finally comes at the end. An awful fate was always on the cards for Howie.
8/10 a 70s classic. Available on Shudder but probably elsewhere too.