While Miss Marple is on vacation in a luxurious Caribbean resort, a fellow guest confides he has evidence that another resident of the hotel is an unscrupulous serial murderer but is poisoned before he can reveal his identity to her.

Aging Major Palgrave, an idiosyncratic but charming mystery writer, reveals to Miss Marple that one of the guests at a luxurious Caribbean resort they're staying at is a Bluebeard-type wife murderer. Unfortunately, the Major succumbs to an apparently accidental overdose of alcohol and blood pressure medication before revealing the killer's identity. When it's discovered that the medicine belonged to another guest and the revealing photograph the Major was carrying is missing, Miss Marple realizes that the serial killer has struck again and more murders will follow.—duke1029