Miss Jane Marple's (Dame Margaret Rutherford's) on-board a train when she sees what appears to to be, a murder - a woman being strangled - in a passing train. When the Police refuse to believe her story, she decides to do some investigating of her own. In this, Rutherford's first appearance (as well as her first on-screen appearance) as Dame Agatha Christie's beloved sleuth. Though fans of the stories can see instantly see that Dame Margaret Rutherford does not fit Dame Agatha Christie's physical description of her, and Dame Agatha was not a fan with the casting decision - at first. But, when the two women met, they became big admirers of each other (Christie even dedicated one of her books; "The Mirror Crack'd From Side to Side" - to her "friend, Margaret Rutherford".