Non si dorme a Kirkwall (1960)

Set on a quiet, windswept Scottish island, the aging and somewhat lazy Pastor Mac Niff requests a curate to help him manage his eccentric parishioners. A young assistant named Newt arrives surprisingly early and begins using hyper-modern, bizarre methods to "save souls." It is eventually revealed that Newt is actually a rebellious devil who has deserted Hell to save humans—not out of goodness, but purely to spite Satan.