Murder Most Foul (1964) - The Blackmailer!

Miss Marple (Margaret Rutherford as Agatha Christie’s sleuth) with her associate Mr. Stringer (Stringer Davis, who was Mr. Rutherford) deducing the meaning of a cut-up newspaper found at a murder scene, ringing a landlady,(Megs Jenkins), and observed by the annoyed Inspector Craddock (Charles Tingwell) Murder Most Foul, 1964.