It’s also worth noting that a recurring theme within the episode is the narrative which rejects death; consider how the episode opens with Moriarty’s reappearance, and Mycroft essentially changing the ending of His Last Vow. Right from the beginning, The Six Thatchers is establishing an inherent ambiguity to that which is true; perhaps most significant of all though is The Merchant of Sumatra, oft-referenced throughout the episode, repeatedly emphasising that when confronted with a story that ended in death, Sherlock didn’t like it – and he changed the ending. Both Moffat and Gatiss are far too precise in their writing for that to be simple throwaway dialogue; it’s a clear statement of both theme and intent.
But another recurring theme throughout The Six Thatchers is the idea that Mary is, in many ways, an equal of Sherlock – as he himself put it to John, “she’s better than you at this”. Time and time again, The Six Thatchers presents Sherlock and Mary matching and surpassing one another, establishing Mary Watson as something of a mirror of Sherlock. What is Sherlock’s greatest achievement? What would demonstrate Mary is his equal, above all else? If Mary were, like Sherlock, able to fake her own death. It’s the sort of move that Moffat and Gatiss would delight in – at the same time both loyal to the Doyle canon, but also gleefully subversive of it.
While I didn’t really like The Six Thatchers on first broadcast, I’ve also been totally unable to get it out of my head for the past week – it’s had a far greater impact on me than any television series I’ve watched in a long time. Indeed, it’s the first programme I’ve watched in years that prompted me to sit down and theorise about the next episode, wondering where it was going and genuinely analysing it – it’s been a long time since I’ve even done that with Doctor Who, frankly.
If nothing else, I’ve now got a lot of respect for The Six Thatchers – surely anything that prompts this level of thought and dissection does, ultimately, have some sort of value. (Although I’ll be pretty annoyed if I was wrong.)
(And I did indeed turn out to be wrong. So that was disappointing.)