The novel, "Sleeping Murder", is Miss Marple's final case. Although written sometime in the 1940s or 1950s, it wasn't published until October 1976, a few months after Agatha Christie's death in January.
The book Hugh Hornbeam is reading his first night in the recently purchased house is "The Little Sister." It is a novel by Raymond Chandler published in 1949 and featuring his private investigator Philip Marlowe.
Parker Brothers released Monopoly in 1935.
Paul McGann and Una Stubbs both appeared in the same episode Doctor Who: The Eighth Doctor: Horror of Glam Rock.
Aidan McArdle starred in Dame Agatha Christie's Sleeping Murder, her last Miss Marple story, and Curtain, her last Poirot novel.