In the last scene, Lewis and Hathaway discuss the concert and Lewis says he prefers Wagner especially if the conductor is Ker-napperts-bush. This refers to a scene in The Remorseful Day in which Morse is impressed by Lewis playing a tape of Parsifal conducted by Fritz Knappertsbusch. Lewis pronounces the name as Nappers-bush; Morse corrects him by saying "we pronounce it Ker-nappers-but-sch".
When "Mad Jack" Macduff dies, his friend and comrade Mungo Coward kisses him on the forehead, exactly as Sgt. Lewis kisses the dead Inspector Morse in the last moment of the final "Morse" story.