In the novel The Moving Finger, Colonel Appleton lived in Combeacre and was around sixty years old. He only makes a single incidental appearance in the book where he was a guest of Richard Symmington and plays bridge there. Colonel Appleton was facinated by Joanna Burton and kept looking at her.
In the ITV 2006 adaptation of the novel (Episode 2, Series of Agatha Christie's Marple), the role of Appleton is expanded. He lives in Lymstock and is among the first to receive an anonymous poison pen letter. In it, the writer states that he knows about Appleton's lechery. Appleton's wife also knew about it and it destroyed her. Appleton was believed to have committed suicide after receiving the letter. His death is the event which brought Miss Marple to the village early in the show--she was an acquaintance and had come to pay her respects. Miss Marple thought that Appleton did not strike her as the kind of person to commit suicide on account of an anonymouse letter. The actor who played Appleton is not credited.