Wanda Ventham and Timothy Carlton, who both appear in this episode, are the parents of Benedict Cumberbatch
Cast members Timothy Carlton and Wanda Ventham are husband and wife.
Laurence Fox and James Wilby were also in the movie "Gosford Park" together.
The only episode where you see Doctor Hobson holding a cigarette, although she specifically states she doesn't smoke.
Laurence Fox (DS James Hathaway) and James Wilby (Hugh Mallory) both appeared on Agatha Christie's Marple: The Sittaford Mystery.