I enjoyed the episode even more after my second viewing.
Both parts of the episode hinged on the power of one mind taking over others. We have Jackson Lake basically giving up his own mind and memories in favor of the Doctor because his grief is too powerful.
They make a point of mentioning that he's missing a lot of the Doctor's memory - he even believes that these Cybermen are the same as the alien Cybermen that he's encountered earlier in his life (while our Doctor very correctly notes that this bunch are humans). He's ever so slightly off, even from the beginning. He's trying to 'be the Doctor' but he's trapped in the parameters of how he actually is. He tells Rosita that investigating the funeral isn't "women's work" and believes that companions will, of course, obey the Doctor. He does his best to have the Doctor's tools in having a 'sonic' screwdriver and a 'TARDIS' of his own, but can only do as much as the current tech of the day allows.
But there's another intensely strong mind in this episode and it belongs to Miss Mercy Hartigan.
We have the Doctor ask about the Christmas date of the 'ascension' of the CyberKing, whether that was her idea (because there is no reason that the Cybermen would care) and she confirms it. I suspect, what happened is that, after they got spanked by encountering Jackson Lake (who became 'the Doctor' to them), they found the strongest mind they could find and made plans to put her in charge (not unprecedented -- they did the same thing with Mr. Lumic, who similarly did not what to turn Cyber... at least, not so soon). They arranged themselves around her desires, including the act of using child labor to power the CyberKing machine -- that's what Miss Hartigan thinks children are good for, so that's what the Cybermen believe children are good for.
Her mind is very powerful and... sadly... fairly broken and warped. The Doctor says of her "you might have the most remarkable mind that this world has ever seen" and she's the matron of a workhouse who is looked down on and ignored by most of society. She's bitter and hurt and wants revenge against a world that feels set against her.
And yet, what she really wants is acceptance -- that's seen in her confused words after the CyberKing rises -- "My people... why do they not rejoice?" She wants liberation; wants to be treated equally and well. And she's brilliant enough to see that it's not going to happen. Since they can't accept her as an equal or even of superior intelligence, she is of the opinion "fuck 'em".
The Doctor 'breaks the Cyber connection', but his words imply that he's done far more than that. "Leaving your mind open," he says. "Open, perhaps, for the first time in far too many years."
The Doctor's regret in the moment before he shoots her is similar to the agony that she feels afterwards. "This is what you make me," he says and he's talking here about every enemy that refuses to back down from a fight and that refuses to let him take any solution but one ending in death. Over and over, he tries to offer people/aliens/creatures a way out of fighting and over and over, they turn him down. Miss Hartigan, as so many others have done, made him a killer (not to downplay, of course, his own responsibility, which he's owned up to more than once) -- her choices also made herself a killer and that is what she realizes. She's become the monster that the world has always been to her.
We also have Rosita, who is ahead of her time the way that the Doctor's companions usually are. She's scrappy and clever and out-spoken.
Here is the Doctor's look after Jackson Lake suggests that Rosita would make a good nursemaid:
(image provided by the wonderful
larissa_j.)
Hee! It's obvious what he thinks of putting her in that particular role. I suspect that Rosita herself is going to teach Jackson quite a bit about how awesome she is. She clearly likes and admires him quite a bit, but I doubt that 'nursemaid' is the part that she envisions herself playing.