Bryony has a secret lover. She has known him all her life and often talks to him—mentally, because she belongs to a family whose members possess the ability to exchange thoughts at a distance. She believes this man is one of her three second cousins, but she does not know for certain, since he has never identified himself, only promising that sooner or later he will reveal himself.
After her father’s death, Bryony returns to the family estate, Ashley Court, and learns that in the last moments of his life her father was trying to warn her of some danger. As she tries to understand the meaning of his cryptic words—“Paper, it’s in William’s brook… Cat, there’s a cat on the floor. Map. Letter...” —the girl begins to realize that her fate is somehow connected with events that took place at the estate almost a hundred and fifty years ago.