It ends with another mysterious woman, another predatory dominatrix older female. She represents another story arc which we, the viewers, have no possibility of guessing or understanding until the inevitable 'twist' becomes self-evident just before being served up to you on a plate several episodes later than it could've been.
She speaks as if she is one of the audience and saw what we saw. Like us, she couldn't see if the Doctor persuaded Half-Face to commit suicide or if he pushed him to his death. Again, a metatextual trick is used as a signifier of
Another physical endurance test or test of skill becomes part of the nature of the monster-of-the-week. The Weeping Angels were based on how long you could go without blinking. The Sredni Vashtar (or whatever they were called) were based on how long you could go without touching a shadow with your own shadow. The droids in 'Deep Breath' were based on how long you can hold your breath (a slightly dodgy thing to encourage in the playground possibly).
How much you like all this probably depends on how much you like repetition.
I said: how much you like all this probably depends on how much you like repetition.
(To be fair, RTD was hardly unrepetitious - how many eleventh episodes ended with robotic things swarming in the sky and swooping down to shoot milling people? Quite a few, as I recall.)
The business with the droids stealing bodies hooks into the corpse economy of Victorian London, but strips it of class significance. Rich and poor alike get predated upon. It's not like in 'Bad Wolf' in which the Daleks harvest the tramps and the sick and the outcasts... and then start feeding on the TV audience which tunes in to watch bodies punished.
The episode has lots to say about faces, and how we acquire them. The Doctor chooses (unconsciously, presumably) his new face as a way of being honest with Clara and trusting her. He initially finds it hard to recognise as himself. Vastra's face is also the key to understanding and accepting her. You perceive a veil if you are unprepared to see and accept who she is. The droid has half a face (why couldn't he have become a Springheel Jack-style urban legend called Jack Half-a-Face? - that would've been awesome) because he unconsciously recognises that it is not his own. He is contrasted with the Doctor and Vastra in that his face is a lie that he essentially rejects despite his attempts to accept it, whereas they performatively reject their own faces as a way of making others accept their honesty.
Vastra's larder mirrors the larder of the droids, their store cupboard of human bits and bobs. It also mirrors the remark the Doctor makes to Clara about all restaurants being slaughterhouses, and his not remembering her becoming a vegetarian. (As a longstanding veggie myself, I liked that bit - though his attitude was condescending... but then, let's face it, the Doctor is often morally condescending, and so are vegetarians.) Vastra's larder is full of human bits and bobs too (its implied) and may even double as her slaughterhouse for killing murderers and harvesting their haunches and sirloin, so to speak. In this she is quite well assimilated into Victorian society, which totally recognised the supposed propriety of slaughtering those found guilty of crimes and then re-using their bodies.
All this business of dismembered bodies, harvesting, cannibalism, absorbtion and the salvaging of human detritus yet again raises the issue of the rendering of humans as mere meat - a perenniel obsession of Doctor Who. And also, the intrusion of the machine into the human body, of the product into the producer, of the fetishized commodity back into the human food chain as both child and dominator.
People really don't understand this show at all. It's like when Shakespeare gets called a 'national poet' or 'sweet swan of Avon' of 'honey-tongued Shakespeare' etc. He's supposedy a poet of love, romance, patriotism, etc... if you read him, he's actually a poet obsessed with hate, cruelty, evil, cynicism, hypocrisy, bombast, bullshit, selfishness, malignant narcissism, internalised self-loathing and failure. Doctor Who is supposed by some to be the 'triumph of romance and intellect over brute force and cynicism'. Wrong. Firstly, much of Doctor Who doesn't even recognise a contradiction between romance and intellect on the one hand, and brute force and cynicism on the other. Secondly, the show is absolutely obsessed with entropy, commodification, fetishism, cannibalism, humans as meat, etc... and that's without getting into even more overt obsessions like class, sadism and tyranny.
The droids in 'Deep Breath' are reverse Cybermen. They are robots harvesting human meat to make themselves human rather than humans creating bionic bits to make themselves robots. This suggests a echoing universal lack of any Aristotelian perfect mean, a correct middle ground. There are only equally horrific extremes which converge from opposite directions... at least when you factor in the conflict between the meat that produces (humans) and the metal they produce. Also implied is a sort of universally unsatisfiable yearning for transfiguration and transcendence. Everyone everywhere wants to be something else, something better.
The road to hell is paved with good intentions. This is standard liberal hand-wringing, especially when you factor in the soft-Dawkinsian stuff about there being no promised land. This is partly a new-Atheist-style rejection of religion (with Missy the evil woman claiming to represent paradise) but also a regulation liberal rejection of the utopian as a form of dangerous extremism. Of course, the utopianism of Jack Half-a-Face is situated within the semiotic scheme of Victoriana and doggerel-Steampunk, so it could be seen as a rejection of the Victorian high-industrial dream of a perfect society acheieved through industry, empire and officially-overseen progress, with morality instilled in thrifty workers and natives via the go-getting top hat brigade.
But he gets impaled on Big Ben... hoist with his own petard? Confronted by his own values? Or skewered by the triumphant expression of human (i.e. British and imperial) superiority?