Nemesis

A letter from beyond the grave. One last request. An unsolvable crime/. When Miss Marple receives a letter from the recently deceased millionaire Jason Rafiel, she's not sure what to make of it. Knowing her deductive skills, he challenges her to solve a crime. If she does so, she will inherit GBP20,000.

The only problem is that he has failed to mention who was involved, or where, and when the crime was committed. Jane Marple is intrigued.