A Candle For The Devil (aka It Happened at Nightmare Inn) (1973)

Eugenio Martín’s A Candle for the Devil (1973), also released as It Happened at Nightmare Inn, is a Spanish psychological horror starring Aurora Bautista, Esperanza Roy, and Judy Geeson. Set in a provincial Spanish town, it follows two sisters who run a guesthouse and impose their twisted sense of morality on female lodgers. Mixing small-town folk horror, religious repression, and psychological dread, the film has become a cult Euro-horror classic.

In a Psycho (1960) inspired thriller from Spanish director Eugenio Martino (Horror Express), Laura Barkley (Judy Geeson) is dragged into a mystery when she arrives at a remote hotel to find her sister missing. Pretty soon more guests, who fall foul of the hoteliers and their draconian religious judgements, find themselves on the missing persons list and the plot moves quickly into a horror of murderous design.

A Candle for the Devil AKA It Happened at Nightmare Inn, is a gruesomely satisfying early 70s piece of exploitation cinema, bristling with dark tension and Giallo-style overtones.

Från IMDB:
Two sisters running a small hotel in Spain kill female tourists whose morals do not meet their strict religious standards.