Christie, Agatha, 1890-1976. Miss Marple mystery.

"Miss Marple receives a postcard from the recently deceased Mr. Jason Rafiel, a millionaire whom she had met during a Caribbean holiday and who had been her greatest ally in solving a murder. He has left instructions for investigating an unspecified crime after his death. If she succeeds in solving it, she will inherit £20,000. Mr. Rafiel hasn't provided her with any details, but he has left her instructions to go on a vacation he has planned for her with a tour group traveling by bus through England and visiting historic homes and gardens. Now, Miss Marple is faced with the ultimate crime ? murder. Someone is quite determined that the past should remain buried. In Nemesis, Miss Marple must solve a crime that not only has no body, no weapon, and no suspects, but no evidence that a crime has even been committed. All she has to go on is one single word: nemesis." -- from publisher's website