Miss Marple receives a request from her attorney, Christian Gilbranson, to pay a visit to his stepmother, Carrie Louise Serrocold, a longtime acquaintance of Miss Marple, at her rural manor. Lewis, Carrie's spouse, privately reveals his suspicions to Miss Marple that someone is gradually poisoning his wife. Soon after Gilbranson's arrival at the estate, he is tragically killed under mysterious circumstances. This sets the stage for a thrilling investigation in the film"Mirror of Death".