Race-horse trainer Bruce Hartley is found bludgeoned to death with a hammer after the Causton Gold Cup race meeting. Bruce, an alcoholic, had threatened to reveal the reason why his father had bequeathed the thoroughbred race-horse Bantling Boy to four Midsomer villagers. The members of the syndicate come under suspicion, and the killing continues when Dr John Osgood, the lover of Bruce's wife Marianna, is also found dead - and even the Gold Cup-winning horse Bantling Boy falls sick. Barnaby and Scott must unravel the secrets of the Bantling family of Bantling Hall to find the killer.