Eerie things are happening at Chelford Castle at night: Since the murder of Abbot Hubert some 400 years ago, his ghost is said to haunt the abbey on dark nights. Devilish howls can be heard as he wanders through clouds of fog. Sergeant Putler, Scotland Yard's most intrepid and successful detective, is hired by Richard Chelford to investigate the case. His older brother, Lord Henry, is much more interested in the legendary treasure of gold that is said to have been hidden somewhere on the grounds since Hubert's death. The situation escalates when Henry's secretary, Mary Brown, disappears without a trace one night, and a man in a monk's habit with a knife appears in Richard Chelford's bedroom, intent on killing him. Meanwhile, Sergeant Putler chases the mysterious monk's terrifying screams through the foggy and eerie night...