Review of The Woman Who Lived
Warning: This review contains episode-specific spoilers and wild speculation about future episodes.
Nominally, The Woman Who Lived was the second half of a two-parter that began with The Girl Who Died. In practice, it's a brand new story featuring the return of a previously seen character, like Craig in Closing Time, the Meddling Monk in The Daleks' Master Plan, or the Master in anything after Terror of the Autons.
There was even a completely different writer for this episode than the previous one; last week's episode was co-written by Jamie Mathieson and Steven Moffat, while this was written by Catherine Tregenna (halle-effin-lujah, finally a woman!). It's hardly surprising, then, that it had a completely different character and feel than its predecessor.
That wasn't necessarily a bad thing. For me, though, the trappings of the mid-seventeenth century, the highwayman known as the Knightmare, and the fine lady in cahoots with Leandro of Delta Leonis (whom I was very disappointed to learn wasn't actually a Tharil after all) were of little interest. They were merely the setting in which the real story took place.
Said real story, as I see it, is twofold. First, there is the fact of don't-call-me-Ashildr's effective immortality, stuck on "the slow path," as Reinette put it in The Girl in the Fireplace. This exploration of what it would mean to live for centuries, outliving everyone you got to know along the way—and not being able to fly off in a blue box after—is the human side of the equation, though a modified one. We are not meant to live so long, certainly not alone. The way Ashildr's perspective has changed, and her attitude toward the lives of others with it, is testament to the psychological effects of that isolation.