Casting Christopher Lee as the hero is such a smart swerve that the film gets a lot of goodwill from me straight away. He plays the Duc de Richleau with such total authority that you barely question the fact he seems to have a sideline in fighting Satanists. Fair enough, it is Christopher Lee. Charles Gray is terrific too, all smooth menace and chilling calm as Mocata. The two of them give the whole thing real weight.
What really sells The Devil Rides Out, though, is the chalk circle sequence. Terence Fisher wrings proper dread out of very little: a knock at the door, some ropey but effective supernatural business, and that wonderfully nasty Angel of Death. It also looks gorgeous in that unmistakably Hammer way, all rich colours, strange light and unapologetically dramatic interiors.
It does wobble when the sillier plot mechanics take over. The romance is limp, one character turn asks for far too much faith, and the ending pulls a trick that made me roll my eyes a bit. Still, this is cult Hammer done with conviction. Not top-tier, but a cracking gateway drug.