Thea Osborne and her trusty spaniel, Hepzie, have been asked by the Montgomerys to look after their house in Blockley while they take a much-needed holiday. Their elderly mother, Granny Gardner, shouldn't be any trouble - although she is slightly forgetful. Thea settles in easily enough, and the arrival of Jessica, Thea's daughter, is a welcome surprise. Granny's behaviour is a little peculiar, but so too are the Montgomerys' instructions to keep her trapped in the house . . . But Thea's got far more to worry about when a body is discovered in the house next door. It isn't long before Thea and Jessica find themselves involved in trying to solve the murder.