A pinnacle of horror filmmaking, this 1973 movie follows a Puritanical English detective investigating a girl’s disappearance on an isolated Scottish isle whose population practice a bizarre ancient religion. Pervasive dread, eeriness and uncertainty make for subtle horror through the first act. The islanders’ practices become increasingly unnerving with each minute. Sergeant Howie is an impressively realized character, who shares our confusion along with his own righteous disgust. Unlike some older horror films, this has held up strongly over the decades, save a couple unintentionally amusing hard zoom closeups and dramatic music cues. And the ending is absolutely devastating.