In a large country house in Derbyshire in April 1809 sits Lady Thomasina Coverly, aged thirteen, and her tutor, Septimus Hodge. Through the window may be seen some of the "five hundred acres inclusive of lake" where Capability Brown's idealized landscape is about to give way to the Gothic style: "everything but vampires," as the garden historian Hannah Jarvis remarks to Bernard Nightingale when they stand in the same room 180 years later. Bernard...