Quick recap
Miss Marple is on a vacation at the Golden Palm hotel, on the Caribbean island of St. Honoré. Chatty Major Palgrave starts telling her about a man who killed several wives and is about to show her a photo, but stops cold when he looks over her shoulder. The next day, he's dead. Miss Marple teams up with the cranky millionaire Jason Rafiel. She realizes the major had a glass eye and was really looking somewhere else: at the couple who run the hotel, Tim and Molly Kendal. The killer is Tim, who had been drugging Molly so her death would look like suicide. Molly keeps the hotel, with help from Rafiel's money.

