The Snowmen

After losing Amy Pond and Rory Williams, the Doctor retires to Victorian England, where Strax, Jenny Flint, and Vastra assist him. The Doctor eventually meets Clara Oswald, a young barmaid with a double life as a governess, to whom he takes a liking. 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.