This episode is a showcase for Vastra and Jenny serving as the Doctor-light and (even more so) companion-light episode of this series, but the true heart of this episode, and the reason this episode makes my list, is Ada Gillyflower - the woman abused by her mother as she selects the righteous to save while planning to rid the earth of the sinful. An outcast herself, Ada finds the Doctor, also a victim of Ada’s mother, in his damaged state and takes claim over him as her “monster.”
"You are all I have, monster, but all will be well. Imperfect as we are, there will be room for us in the new Jerusalem."
Given that our core cast of this episode includes two lesbians, an alien who has committed great atrocities despite being a good man, and a damaged woman being told she is sinful, the point made here that there is room for the imperfect in the new Jerusalem is an important one.
The villain of this episode is the woman destroying people with a fake sense of righteousness and justice while the imperfect people are the heroes.
Vastra and Jenny aren’t immune to the society they live in but don’t let it victimize them as they have knowledge that the world is both greater and stranger than the Victorian Values around them and largely treat this as another case to solve in a messed up world. On the other side of the case, Ada and the Doctor are caught in the middle of it and unfortunately, Ada believes her mother’s words until the very end.
The emotional damage left on this woman by her mother manages to outweigh the physical scars she suffered in being used as an experiment. Not only did her mother cause her injuries, she made her think that her father drunkenly hurt her because she was sinful rather than telling her the truth. So, she turns to the Doctor, a monster even more disabled than herself, for comfort.
Ada goes through such a range of emotions in this episode - from the beaten down victim to the vengeful woman who tries to reclaim her life upon learning the atrocities committed to her by her mother. Spending so much of her life as victim, Ada does not instantly recover, but we’re left with the sense that she will be fine. We’ve seen the inner strength she’s capable of.
And the Doctor’s relationship with her is nearly perfectly portrayed. She took him in as a monster where he witnessed her true character and in return he treats her with such respect and kindness. He may no longer look like a monster by the end of the episode, but if there is one thing we know about the Doctor it’s that he often does feel like a monster for the things he’s done. It’s easy to see how he sympathizes so deeply with Ada - the outcast who tried to save her monster.