Nemesis by Agatha Christie

Even the unflappable Miss Marple is astounded as she reads the letter addressed to her on instructions from the recently deceased tycoon Mr. Jason Rafiel, whom she had met on holiday in the West Indies (A Caribbean Mystery). Recognizing in her a natural flair for justice and a genius for crime-solving, Mr. Rafiel has bequeathed to Miss Marple a £20,000 legacy -- and a legacy of an entirely different sort. For he has asked Miss Marple to investigate...his own murder. The only problem is, Mr. Rafiel has failed to name a suspect or suspects. And, whoever they are, they will certainly be determined to thwart Miss Marple's inquiries -- no matter what it will take to stop her.