A woman on a train tells Miss Marple about a series of murders in her village. When the woman later falls to her death, Miss Marple vows to get to the bottom of the string of “accidents.”

During a chance encounter with a fellow passenger on a train, Miss Marple (Julia McKenzie) hears about a string of murders in a peaceful village town. When Miss Marple learns that the passenger is involved in a tragic accident before making her report to the police, she decides to investigate further to track down the killer, unearthing secrets about the village and its inhabitants.