In 1921, in London, the arrogant and skeptical Florence Cathcart is famous for exposing hoaxes and helping the police to arrest con artists. The stranger Robert Mallory tells her that the headmaster of a boarding school in Rookford had invited her to travel to Cumbria to investigate a ghost that is frightening the pupils to death. He also tells that many years ago there was a murder in the estate and recently pupil Walter Portman had died. The reluctant Florence finally accepts to go to Cumbria....