Miss Marple receives a post card from the recently deceased Jason Rafiel, a millionaire whom she had met during a holiday on which she had encountered a murder, which asks her to look into an unspecified crime; if she succeeds in solving the crime, she will inherit £20,000. Rafiel, however, has left her few clues, not even when or where the crime was committed nor who was involved. Her first clue is a tour of British famous houses and gardens, arranged by Mr Rafiel prior to his death. She is accompanied on the trip by fourteen other people, at least one of whom she suspects to be related to her enquiries. She learns that one of her companions, Elizabeth Temple, is the retired headmistress of the school which a girl who was engaged to Rafiel's ne'er-do-well son, Michael, attended. Another member of the tour group, Miss Cooke, is a woman she had previously met and discussed gardening with.