One year ago, seven people sat down to dinner. One of them, Rosemary Barton, never got up. She was thought to have committed suicide due to a post-flu depression. When her husband, George, begins receiving anonymous letters saying that Rosemary was murdered, he decides to investigate. He reconstructs the fateful dinner precisely, invites the same people, and hires an actress that looks like his wife to play her role. The actress does not arrive...