To promote the special , three prequels were released . The first was broadcast during the 2012 Children in Need telethon on 16 November 2012 , titled " The Great Detective " . The Silurian Madame Vastra , her human wife Jenny Flint , and the Sontaran Strax ( all returning from " A Good Man Goes to War " ) describe a number of strange phenomena to a shadowed fourth detective . The fourth detective reveals himself to be the Doctor , and tells the group that he has retired .