Joan Alder, the local composer of a very successful piece of music, 'Midsomer Rhapsody', died twenty years ago, leaving bitternesses among her family. Barnaby and his wife know her mother, Peggy Alder, who is about to remarry. A local man is murdered, and Barnaby realises that he was her music teacher. Then a valuable manuscript shows up among the murdered man's effects, that appears to be an early draft of the work as a collaboration by two hands, but Barnaby suspects it is a forgery, by someone who hopes to gain a share in the continuing royalties. Then Joan's long-lost daughter, Sarah Douglas, appears, followed by the revelation that her boyfriend, who was thought to be dead, is living close by. As the number of people with an interest in Joan Alder's work increases, the number of those interested in her work decreases as further murders occur.