Vastra Investigates: A Christmas Prequel was a webcast and prequel produced for the 2012 Christmas special. It was the second prequel to The Snowmen to be produced, after The Great Detective, which aired in November during Children in Need.
Madame Vastra, accompanied by her loyal companions Jenny Flint and Strax, is called upon to investigate a Victorian murder mystery. But where is the Doctor?
Another case has been cracked by Madame Vastra; Strax keeps the criminal secure while a Scotland Yard officer, Inspector Gregson, thanks Vastra for her help, commenting how odd Strax looks. Vastra explains the Sontaran's origins, and hers as well when he asks if the skin condition hurts, mistakenly believing her to be human. She perplexes him further by saying she fell in love with her assistant Jenny Flint. Departing in a carriage, both are saddened that the Doctor appears unwilling to leave his TARDIS. However, they then both notice something very odd: it is snowing, yet there are no clouds in the sky...