Jason Cavendish (Donald Pleasence) is a British professor who has written a popular children's novel. Living with his family and loyal butler, Mr. Hill (Denholm Elliott), in a remote mansion, Cavendish isn't used to visitors, but he receives one unexpectedly in the form of Daniel Young (Tom Conti), a student working on a thesis involving the author's work. Soon, however, it's clear that people aren't who they appear to be, and mystery and murder are part of the puzzle