The Snowmen

After losing Amy Pond and Rory Williams, the Eleventh Doctor has retired to Victorian England, where Strax, Jenny Flint, and Vastra assist him. The Doctor eventually meets Clara Oswald, and takes a liking to the young barmaid who leads a double life as a governess. At the same time, a sinister plot is unfolding; snowmen are randomly appearing around London, growing in size and power. All they need to take over the world is some human DNA in ice crystal form, and the frozen body of a drowned governess can give them just that.