The Owl Service (1969)

Alan Garner adapted his own novel, and the result is still the template for folk horror on television. Three teenagers staying at a remote house in a Welsh valley find a dinner service whose floral pattern, pieced together, forms an owl, and they start reliving the legend of Blodeuwedd, the woman made from flowers and turned into an owl. The rivalries of class and family between them do as much work as the myth. It went out in a Sunday afternoon family slot, yet the tone is strange and adult, so expect slow-building unease rather than shocks.