Old miss Marple is on a train ride when she witnesses a murder in a passing train. She reports it to the police but they won't believe her: since no body can be found there can't have been any murder, right? As always, she begins her own investigation. The murder was committed while passing Ackenthorpe Hall and miss Marple gets herself a job there, mixing cleaning and cooking while searching the house for clues.
Jessica Fletcher,一名有能力解决谜团的著名神秘作家兼一位英文代课教师。有无数的命案发生在她周围的朋友,侄儿及他家乡的邻舍。她的朋友,Dr Seth Hazelet,和一位警官,Amos Tupper,时常协助她调查命案。有时,Jessica 会在剧放映前来一断开场白来介绍本集故事。过后,Jessica 搬迁到纽约城市出版更多接触于命案的发生的故事。