Morse says near the climax of the episode that Nicholas Myers sends out the "twilight bark" which is a reference to barking of dogs that sounds the alert about the missing puppies.
When DI Thursday discusses leaving the force because of a proposed restructure of local police forces he refers to an officer called McNutt as a potential ally/colleague for Morse. The character McNutt appears in the "Inspector Morse" story "Masonic Mysteries" as a vicar, retired from the force (played by Ian Cuthbertson).