 When Rachel Argyle is found dead in her study, her son Jacko is found guilty of her murder and hanged. He was deeply in debt and had a terrible row with his mother just an hour and half before she was killed. She had refused him any money and he threatened to kill her. Several years later, Gwenda Vaughn is engaged to the now widowed Leo Argyle and she invites her friend Miss Marple to the wedding. When the family learn that Jacko s alibi was genuine, they must deal with the fact that an innocent man was executed and that the true killer is still free. Miss Marple assists her friend in identifying the true killer but not before someone faces a tragic end.