The novel "4.50 from Paddington" features which fictional detective?

"4.50 from Paddington" is a detective fiction novel by Agatha Christie, first published in November 1957 by Collins Crime Club. This work was published in the United States at the same time as "What Mrs McGillicuddy Saw!", by Dodd, Mead. The detective and protagonist of the novel was Miss Marple.

Miss Marple is a fictional character in Agatha Christie's crime novels and short stories. Jane Marple lives in the village of St. Mary Mead and acts as an amateur consulting detective. Often characterized as an elderly spinster, she is one of Christie's best-known characters and has been portrayed numerous times on screen.

Her first appearance was in a short story published in "The Royal Magazine" in December 1927, "The Tuesday Night Club", which later became the first chapter of "The Thirteen Problems" (1932). Her first appearance in a full-length novel was in "The Murder at the Vicarage" in 1930, and her last appearance was in "Sleeping Murder" in 1976.