A woman is murdered on a train. When Miss Marple telephones her friend Lucy Eyelesbarrow and asks her to go undercover to investigate, Lucy quickly accepts the challenge!

Who is the dead woman? What was the motive for her murder? And why was the body thrown from the train and later hidden at Rutherford Hall?

When a second murder takes place, everyone at Rutherford Hall seems in danger, so Miss Marple sets a trap to catch the murderer.