Thus far, the loose theme of this season of Doctor Who seems to be "identity crises" and "deconstructing heroism." These themes manifest this week in another story where the Doctor isn't entirely calling the shots, and the main McGuffin that everybody is trying to steal is "selfhood." Spoilers ahead...
The central mystery at the heart of "Time Heist" is not really much of a mystery at all: the identity of the figure known as the Architect who has hired the Doctor, Clara, a hacker named Psi and a shapeshifter named Saibra to break into the most secure bank in the universe. Of course, the Architect is the Doctor — the answer to every mystery on this show nowadays is usually "the Doctor."
But in fact, the Architect/the Doctor is really just a puppet in himself. The real mastermind behind all of the events of this outing is Miss Karabraxos, the owner of the Bank of Karabraxos who's staffed the bank with disposable clones of herself like the beleaguered Miss Delphox. The present-day Miss Karabraxos is another snooty boss lady, cut from the same cloth as Missy, Miss Kizlet from "Bells of St. John" (and arguably Vastra and River Song to some extent.)
But even though Miss Karabraxos is a ruthless Thatchery exploiter in the present day, years in her future she winds up regretting her evil ways. And in one of the closed-loop paradoxes that are the show's stock in trade of late, she thinks back to the day that her bank was destroyed by a sudden solar flare. (Somewhat careless of her to build such a secure bank in such a vulnerable spot, really.) And she decides to contact the Doctor, who told her that he's a time traveler back then, and cook up a plot for the Doctor and friends to break into her own bank in the past and free the Teller, the creature she mistreated there.
In essence, in this story, Miss Karabraxos is Sally Sparrow from "Blink," and the Doctor is her puppet, pretending to be the puppeteer.
And I guess Miss Karabraxos, having created a whole institution named after herself and in her own image, full of duplicates of herself, is trying to reclaim her own identity as much as all of the other characters in this story.
Anyway, the Teller is the show's monster, but it's also a victim in need of rescue. The Teller has the power to detect guilt psychically — which is why the Doctor and his friends inflict amnesia on themselves at the start of the story — and when it finds a guilty party, it siphons off someone's mind, leaving a horrific empty husk with a caved-in-looking skull. At one point, the Teller catches up with Clara, and the Doctor issues the injunction "Don't think!" (which joins "Don't breathe," "Don't blink," "Don't turn around," and various others. This show should have an episode called simply "Don't".)
But the Teller is in chains, and is clearly being used rather than being a willing participant in all of this fiduciary naughtiness. And indeed, it turns out the vault the Doctor has to break into contains not riches or secrets, but the Teller's mate who's been imprisoned as further leverage. The Teller gets to be free and happy with its girlfriend, instead of being an unwilling monster who robs other people of selfhood.
The "reclaiming your identity" theme is underscored by the storylines of the Doctor's two accomplices. Saibra becomes anyone she touches, but that means she can't touch anybody without losing herself (until the Doctor helps her find a cure.) And Psi had his memories of his friends and family deleted to protect them when he went to prison (until the Doctor helps him restore them.)
And the "hook" that kicks off the whole zany story is the Doctor and friends having their memories erased using mind worms, making you wonder what's really going on, and if the Doctor is really being heroic or a tool here. (Spoiler: the Doctor is really being heroic. But he's also kind of a puppet, as discussed above.)
It's somewhat traditional, after a regeneration, to have a brief moment of the Doctor questioning his identity — but we're now on the fifth story in a row where the Doctor's Doctoriness is put to the question. Is he a good man? Is he as worthy as Robin Hood? What's he afraid of, and how does this define him? And now, we get "can he be trusted?" I'm curious to see where this is headed — I guess we're supposed to think the Doctor is questioning himself after hundreds of years on Trenzalore, but I still haven't really felt the weight of that time other than as a brief montage. (The centuries on Trenzalore feel as weighty as the centuries spent running from the Silence, I guess.)
If I had to guess, I'd say we're leading up to the Doctor finding a way to restore Gallifrey, and then questioning whether he's doing the right thing. That seems to be the main shoe that Moffat has left hanging in mid-air, and the fact that there's been zero mention of Gallifrey since Matt Smith's finale makes me think it's going to be some kind of big reveal. I'd bet on that being the point of the Missy/Paradise stuff, somehow. (Although her "Paradise" reminds me a bit of the V.R. afterlife where the Doctor stranded River Song.)
All in all, "Time Heist" was sort of fun. For a story whose "hook" is amnesia, it's actually somewhat forgettable. But Peter Capaldi continues to have the gift of elevating whatever material he's given, just through the power of sheer conviction. I guess it's sort of funny that we're getting a Doctor who constantly questions himself, even as he's played by the actor who's most capable of effortlessly owning the authority and character of the Doctor of any we've seen in the new series.