4:50 from Paddington

4.50 from Paddington was first published in the United Kingdom in November 1957 by Collins Crime Club and appeared in the United States at the same time under the title What Mrs. McGillicuddy Saw!. It was serialised before publication in both countries, which was the usual arrangement for a Christie novel by this stage of her career, and it is one of the Miss Marple books written in the period when she was publishing roughly a novel a year.

The premise is a timetable problem. A murder is committed on a moving train by a person who knows the rail network well enough to plan the disposal of a body, and the solution is worked out through a survey of a country estate, a set of connections between two lines and the discovery of what has been buried where. Christie uses a young assistant to do the physical work, and Miss Marple sits in the village asking apparently irrelevant questions until the shape of it appears.

The novel was adapted into a film in 1961 as Murder, She Said and has been filmed for television several times since, including a 2004 adaptation with Geraldine McEwan. It is the kind of Christie plot that readers describe as the reason they keep returning to her: an eyewitness who is dismissed, a crime that the police assume never happened, and a solution that turns entirely on the geography of the line.