Accusations of unsportsmanlike conduct on the river are bedevilling the Midsomer game fishermen, and Barnaby has to interview elegant widow Isobel Hewitt, a spendthrift, fast-living, Jaguar-driving 75-year-old, when another lady fly-fisher accuses her of a violent assault. Then first Isobel and later her fellow villager Dr Duncan Goff are found on the river-bank with their skulls smashed in, and there is no shortage of suspects - including an antique dealer who apparently specializes in befriending elderly widows. The picture is confused when one of the suspects, chef-restaurateur Keith Scholey, is found frozen to death in his walk-in deep freeze, with the lock of the door jammed by a nail. Troy has a theory that Scholey was the killer and has made his suicide look like murder, but will that be the end of the affair?

Barnaby investigates a death which looks very much like suicide. The dead man was a troubed and depressed gambler on a losing streak, but Barnaby's nose tells him to look for a murderer. During the investigation he recognizes someone from his past, in the shape of Dr Jane Moore.

Someone is decimating the ancient Smythe-Webster family of Upper Walden, and the bad blood between the villages of Upper and Lower Walden is renewed with a vengeance. First, young heart-throb actor Larry Smith (alias Laurence Smythe-Webster) dies in an explosion at a publicity event for a new film. House of Satan is based on a book by a local writer, the late Ellis Bell of Lower Walden - a village whose inhabitants are referred to by its Vicar, the Reverend Simon Smythe-Webster, as ""the weasels of the wild wood"".The next to die is Larry's uncle, House of Satan producer Frank Webster (Francis Smythe-Webster), electrocuted to death on his exercise bike. Finally, Barnaby's principal suspect, Danny Pinchel, the family's cook, is drowned in a large bowl of tomato soup...Barnaby realizes he is dealing with an historic grudge, and he enquires into the family's antecedents.

Julian Shepherd, who has most of his money invested in Charles Edmonton's new invention, is found drowned, and there is every appearance that he killed himself due to money problems. Then a villager who has been stealing peregrine falcon eggs from Charles's widow is also found dead, and Barnaby and Troy investigate.