Madame Vastra is a female Silurian warrior, who had awoken during the construction of part of the London Underground in the late 19th Century. She had sought revenge on those responsible of the deaths of her "sisters," but was convinced not to give into her rage by the Doctor.

"Was I being insensitive again, dear? I don't know why you put up with me."

Instead of killing innocent people, Vastra made a home in London, hiding her Silurian form from people, and acting as a freelance crimefighter. Along with Jenny, her Maid and trusted companion, she hunts and disposes of the evil in London. While she keeps her identity a secret, there are a few people who know who and what she really is.