This enjoyably unusual combination of Agatha Christie-style murder-mystery and gothic chills was the brainchild of Amicus Productions, Britain's chief rival to Hammer Films during the golden era of 1970s Anglo-horror. The film is best known for its gimmicky 'werewolf break' towards the end, where the audience is given 30 seconds to guess the werewolf. But there's much more to enjoy here, not least a sterling case including Calvin Lockhart (a rare Black lead for a British horror of the time), the ubiquitous Peter Cushing, and small roles for Charley Gray and Michael Gambon.