When Doctor Who's penultimate episode ended last week, fans had more questions than ever. How was the Boundary connected to Gallifrey? Who or what was the Timeless Child, how were Yaz and Graham going to survive being trapped on a Cyber war carrier, and what was that weird Ireland based story? The good news is, the Master stepped through the Boundary, demanding the Doctor take his hand so he could explain a few things.
The Doctor: Have you ever been limited by who you were before?
The Doctor follows the Master into the ruined Citadel, as he reminds her, at every turn, of their shared childhoods. There's a reason for that, it turns out, as the Master locks her in paralysis and sends her into the Matrix Chamber, the one place he hasn't destroyed. The Matrix is the repository of all Timelord knowledge, and inside, the Doctor will learn that childhood was all a lie. But first, the Master wants to show her how Timelords came to be. It's time for a Gallifrey history lesson.
Like Earth, Gallifrey was a small backwater planet, whose indigenous people, the Shobogans, slowly achieved technology and space travel. Tecteun (Seylan Baxter) was the first of the Shobogans explorers to go into space. On her travels, she discovered the Boundary. Beneath its purple glow, there was a child, lost, alone. Tecteun took her home, raised it as her own, all the while studying the girl to learn what race or species she was. Then one day, tragedy struck when the girl fell off a cliff and died. Except the child didn't die, she regenerated. Tecteun's mind was blown.
She spent decades trying to understand what regeneration was and how to replicate it. It took decades of Tecteun's life and countless regenerations of this "Timeless Child" before she figured it out. But once she did, she gene-spliced it into herself, and then into the ruling class of Shobogans, until they too could also regenerate, 12 times in total. These Shobogans restyled themselves, based on their new ability, renaming their race "Timelords."
The Timeless Child went on to become part of their Security Division, living many regenerations, always erased, so no one would suspect she was different than the others. The latest batch began a few thousand years ago: William Hartnell, Patrick Troughton, Jon Pertwee, Tom Baker, Peter Davison, Colin Baker, Sylvester McCoy, Paul McGann, John Hurt, Christopher Eccleston, David Tennant, Matt Smith, Peter Capaldi, and now Jodie Whittaker. The Doctor. Our Doctor. She's the Timeless Child. Her story was Brendon's story, draped in metaphor within the Matrix so that the casual Timelord historian wouldn't notice it. How many other of her selves are out there, forgotten, erased from her mind? Jo Martin is one, but there are so many others she's yet to find.
So that's one mystery solved, but what about the Cybermen and the Master? While The Doctor is learning how much she's been abused and used (and the Master is ranting how the Timelords are frauds), the Companions are showing two years on the road have taught them survival. Trapped on the carrier, Graham comes up with the idea of disguising themselves as Cybermen. This way, they can both escape the ship and save Ryan down on the planet. Once reunited, Yaz leads the team, along with survivors Ravio, Yedlarmi, Ethan, and Ko Sharmus, through the Boundary to save the Doctor. (It's their turn to save her.)
Meanwhile, the Master has lured the Lone Cyberman and his troops to Gallifrey as well. He promises to welcome them as conquerors, but he plans to shrink the Lone Cyberman and his "Death Particle" down to size (miniature size!) and steal the Cyberium for himself. With the power of all Cyber knowledge and all Timelord knowledge, plus a whole lot of Timelord bodies on ice downstairs, he creates an unstoppable army of hybrid CyberMasters, with the ability to regenerate and the desire to destroy all human life.
It's a lot to solve in the last 15 minutes, but after a pep talk from Jo Martin's Doctor, ours is up to the task. The Lone Cyberman's "Death Particle" was supposed to wipe out all organic life across the universe if detonated. But now that's it's miniaturized along with his body, it's only enough to take out a planet. That'll be enough to wipe out the CyberMasters, and all life on Gallifrey. The Doctor stashes the surviving humans and her fam in a spare TARDIS and sends them home to Sheffield. But before the TARDIS takes off, Ko Sharmus, who was part of the team that sent the Cyberium back in time to Shelley in the first place, follows her out. He takes her place and sacrifices himself to take down the CyberMasters, while the Doctor escapes in a different spare TARDIS.
Yaz, Ryan, and Graham have survived their adventures. They are now home, perhaps for good. The new TARDIS takes on the form of a regular Sheffield home, so Ravio, Yedlarmi, and Ethan have a place to start life in a time and place of (relative) peace. The Doctor also makes it back to her TARDIS, with a newly expanded knowledge of self, ready to take on the universe once again. But before she can pick up her friends, the Judoon materialize in front of her. They've finally caught up to the Doctor, imprisoning her for her crimes. As the season ends, the Doctor finds herself in a Maximum Security facility, deep in space, with a life sentence and no one to rescue her. (I'm not saying it's the Stormcage Containment Facility, but that *would* be handy.)
On the one hand, this rips up the entire rule book. When the Doctor arrived on Earth, he was "The Last of the Timelords." Now, in a retcon that's going to shake the fandom to the foundations, it turns out she was the first of them. It's a genius way to expand the canon. (Also check that scene where she blows the Matrix, it includes the "Morbius Doctors," bringing in some canonical loose ends from Classic Who.) It also gives any companions who might need to go off and star in an American TV series an out, one that doesn't kill anyone off. (Though we've not seen the last of them, Yaz, Ryan, and Graham are confirmed for the "holiday special" this winter, "Revolution of the Daleks.") Older fans will doubtlessly howl in rage, but as far as I'm concerned, the possibilities just became endless as we await Season 13.