Elspeth McGillicuddy's claims of having witnessed a woman's murder on the train alongside her own are put down to day dreaming by the police, with no body found, and no other witnesses. Only Miss Marple believes her friend's story, and starts her gentle digging into this complex and deadly case.

I'm not sure what to make of this mystery. Miss Marple places herself as largely a background character due to her ailing health and old age; instead, establishing a trusted housekeeper as the sleuth. While Miss Marple's wit is amazing in narrowing down the secondary crime scene and the suspect's home, this seems to be where the sleuthing ends and much of the story becomes character studies and daily living. Further crimes are committed, but these don't seem to be actively investigated by Miss Marple or her "agent", with the story plodding along uninteruppted.