Doctor Who's "Spyfall, Part 1" ended with The Doctor trapped in the green place and Ryan, Yaz, and Graham on an airplane, the engine of which has been blown off. How will they survive this nasty death? Well, it starts with a glass and metal square labeled "Ryan, " which leads to another square, this time with a helpful left arrow, and that leads to a seatback pocket with the most helpful thing of all: Pictograph instructions of "How To Land A Plane Without A Cockpit."
Doctor: Two pacifists and a 19th-century descendant of Byron, against the Nazis in Paris and an alien invasion across multiple dimensions. That's a big to-do list.
The Doctor, meanwhile, found a friend. Her name is Ada (Sylvie Briggs), and she believes this is the inside of her mind, and the aliens, the "Kasaavins," are guardians. She takes the Doctor home with her to 1834, where it turns out she's Ada Lovelace (actually, Gordon, she hasn't met her nice Earl yet), and this is a scientific symposium where inventors are hawking their latest steampunk-ish inventions. Considering the surroundings, the Doctor telling Ada she's a time traveler investigating a 21st-century conspiracy doesn't sound out of place.
Onboard the Master's TARDIS — the Australian farmhouse, flying through the Time Vortex, not unlike the Wicked Witch of the West's house in a tornado — Barton is super upset to learn the companions are alive and the plane's landed in Essex. Even with him on their tail, the companions, devoid of both Doctor and internet (so Barton can't track them), do well, asking the right questions, and continuing to keep the planet safe. And they still have some of the Bond tech from last week to defend themselves when the Kasaavins attack.
The Master, arriving in 1834, is super upset to learn the Doctor's still alive. The Doctor is delighted to discover the Master doesn't know about the green place, as Ada rigs up a Gatling gun and shoots him out of the room. Her pal, Charles Babbage (Mark Dexter), takes them home, where the Doctor realizes meeting them is no accident. Babbage has a sculpture, the "Silver Lady," sent as a token of appreciation from a young man from his "Master." It projects Kasaavins. These creatures aren't just alien spies in space, but through time, following Lovelace for a decade from the green place — their dimension.
So the Doctor fires the Silver Lady up, hoping to use it to get back to the 21st century. There's just one small hiccup — Ada grabs her hand again. The Kasaavins, like the TARDIS, are not as stable in this dimension as they would like. The Doctor and Ada end up in Paris in 1943. Luckily they're picked up by Noor Inayat Khan (Aurora Marion), Britain's first Muslim war heroine, who tucks them away under her floor as the Nazis, led by the Master, come looking for them.
Khan's radio equipment gives the Doctor a way to communicate. But the first person she calls, of all people, is The Master, for them to meet on the Eiffel tower. She's distressed by the Nazi outfit — that's low, even for him. (Missy would never.) He confirms the Kasaavins were already here on Earth, sleeper agenting across our dimension, watching over those who would eventually invent computers to make sure they aren't going to attack. He convinced them the planet was dangerous. But it's not because he wants to kill humanity. He was just trying to get the Doctor's attention to tell her something: Gallifrey has been destroyed.
While the Doctor records their convo, Lovelace and Khan track down the farmhouse, sitting in the middle of a Paris alleyway. Now the Doctor has a way home, the evidence she needs to convince the Kasaavins not to attack, and all the answers. Meanwhile, viewers will not be surprised to learn Barton now owns the Silver Lady sculpture seen in Babbage's home, an antique he's so proud of, he's showing it off to his mum. She's not impressed, probably because she's been kidnapped and tied up in a warehouse, though he thinks it's because he moved to America on her. (Family drama!)
By the time the companions reach Barton, he's moved on to a keynote speech, where he declares us "way past peak human." The plan with the Kasaavins is to repurpose humans as hard drives, a la The Matrix. Those spies who were "wiped clean" proved reformatting worked. Now Barton will send Kasaavin energy via an app all devices to wipe everyone else. (Permission to do this was in the updated Terms of Service.) The Master walks in, ready to see his plan put into action after slow pathing it through the 20th century. But the Doctor took a faster route, stopping to throw a failsafe into the Silver Lady to stop them, before banishing the Kasaavins to their own dimension, and the Master with them.
The companions are a little shaken. How did she save them from the plane? Who are these new companions? Are they being replaced? The Doctor gets a little wide-eyed, and off she pops, to rig up the plane and return Ada and Noor home. But before she returns, she heads to Gallifrey to see if the Master was telling the truth.
He was. Not only that, he's left The Doctor a confession: He did it. The Master swears it was for a good reason. He had to make them pay -- the Founding Fathers of Gallifrey lied to them. Lied about everything, built on the story of "The Timeless Child." If that sounds familiar, it should — it was the dangling plot thread left from Season 11, Episode 2, "The Ghost Monument," when the Remnants freaked the Doctor out by mentioning it. "We see deeper, though, further back. The Timeless Child… we see what’s hidden, even from yourself. The outcast, abandoned and unknown..."
Doctor Who brought back the Master, but the companions have started demanding answers of who their Doctor is. It seems to have brought back a season arc this time too.