Simon Hannaford and his sister Laurie are left in charge of their aunt's estate near Oxford while she travels abroad; to settle some debts, Simon decides to sponsor a murder-mystery weekend for well-paying guests. It soon appears that everyone at Madingley Grange has arrived with ulterior motives, including the temp-service staff who are casing the place with an eye to burglary. When Derek is chosen victim, much to his voluble distaste, and then is found actually murdered the next day, Simon and Laurie's problems really begin.