John Steed begins to be the victim of frightening nightmares that are constantly repeated, everything turns out to be the product of an organization that uses the telepathic powers of its members to enter his psyche and manipulate his behavior. The nightmares that incorporate a sinister Santa Claus, divergent mirrors and guillotines, the old castle with a costume party themed on the characters of Charles Dickens and the table of spiritualism make this episode one of the darkest and scariest of the entire series serie.