We zoom around an empty castle while the Doctor voiceovers about how from the moment we’re born our death pursues us, blah blah blah, mortality, whatever. Then a hand pulls a lever and falls into some sand and dissolves. The Doctor appears in a human-size pneumatic tube in the room where the hand just dissolved, like a special delivery from hell. He examines the sand and then gives a big speech about how if the person who brought him here had anything to do with Clara’s death he’s going to make them rue the day and you know it’s basically just this:
He roams around the corridors a bit, grandstanding about how scared whoever brought him here should be, until one of the many static-y flatscreen TVs peppered around the walls turns to footage of the Doctor, seemingly filmed through a window across the courtyard. He looks out the window and sees a veiled figure, and despite talking to himself at length about what a badass he is just a moment ago he is immediately terrified and starts running away.
He gets stopped by a locked door and the veiled person, who is surrounded by a swarm of flies, comes toward him with creepy decomposing hands outstretched.
The Doctor is like “Oh you know, this is nbd, I just have to make a psychic link with this door so it will open for me!” and he talks to it about how he understands how sucky it must be to be a door and he understands its pain and then the door opens because this is Doctor Who and there is nothing too ridiculous. But unfortunately for him, there is a wall directly behind the door. The hooded creature is now right up in his face and he’s like “HOLY SHIT, I’M AFRAID TO DIE!”
Then suddenly the figure and the flies all freeze in place and the Doctor is like “?” and looks out the window and sees that the castle is circular and clock-like and the different floors start spinning in different directions, causing the wall behind him to move out of the way. The whole castle setup gives off a very Ocarina of Time Forest Temple vibe tbh. Anyhow, the new door reveals a pretty nice looking bedroom that I would be willing to give a decent rating on TripAdvisor depending on the price.
He goes into the room and tests out the bed and sees there’s a giant portrait of Clara’s beautiful face on the wall. He examines it and sees that it’s, in his own very precise words, “very very old” because the paint is cracked and flaking. He is too distracted by how pretty she is to notice that his cloaked friend has joined him until it’s basically right on top of him again. He realizes that the creature is actually a figure taken from his nightmares: an old lady who died when he was little who was in a funeral shroud but still surrounded by flies because it was hot outside and her decomposing flesh was too pungent. He’s like “I know I said I’m afraid to die and that’s true, but WATCH THIS!” and then he throws a stool through a window and jumps out into what seems to be a bottomless abyss.
JK! While he falls, he uses his super Time Lord intelligence to go to his mental happy place (inside the TARDIS with Clara (*sniff*)) to figure out a survival plan. He pretends that he’s explaining to Clara (who is standing in front of a chalkboard with her back turned) how he survived after the fact to impress her, and in the process figures out that the castle is on the ocean and he knows exactly when he’ll hit the water based on when he heard the stool he threw hit it. Some questions start showing up on the blackboard like “Wheretf are you, howtf did you get that veiled jag to freeze, and howtf are you going to get out of this mess?”
The Doctor IRL meanwhile is floating underwater like “I dunno” but he opens his eyes and sees that the ocean floor is covered in skulls so he Gs TFO of there and into the central tower of the castle. Where, much to his surprise, he finds himself in a cozy little room with a fireplace next to which exact replicas of his snazzy velvet suit and sensible boots are sitting nice and dry for him. He hangs up his wet clothes exactly where he found the dry ones and heads back into the castle without seeming to spend much thought on this bizarre turn of events.
He comes across a room with an octagon shaped depression in the floor with chalk arrows pointing at it (spoiler alert: by the end of the episode I still have no clue what the point of this thing is). There’s another TV showing where the hooded dude is and the Doctor is like “Oh I sort of get it maybe? This is a haunted house prison and you’re trying to scare me to death, whoever you are!” He goes out into a spooky garden full of brambles and shit and finds a nice rectangle of recently piled dirt and a shovel. He consults his mental Clara and decides to dig for a while and find out what the deal is.
While he digs, the creature catches up to him and he manages to wedge the door closed with the shovel. The creature is like ¯\_(ツ)_/¯ and wanders away for long enough for the Doctor to get to the bottom of the very gravelike hole, where he finds the words “I am in 12” written on a slab. He doesn’t get to think about that for very long because the creature suddenly appears out of nowhere and waves its creepy hands near his face. He goes back to his mental TARDIS to figure out how to stop it and determines that he has to tell it something true that he’s never told anybody before. The first time it was that he was afraid of death. This time he tells it that he didn’t leave Gallifrey because he was bored, he left because he was scared.
The creature stops and then the castle does it swirly thing again and the Doctor starts trying to figure this shit out in earnest. He learns that by running real far he can buy himself about an hour of time to work on finding Room 12, where he assumes he’ll find… something. Then he runs from the creature again and does some more work. It seems very tedious and he’s worried he’ll have to be there forever.
One day he finds himself back in the pneumatic tube room but this time there’s a skull on the floor which he picks up while musing in voiceover about death and birth. On the floor there’s some sand with the word “bird” written in it. The Doctor is like “Bird? Huh?” My personal theory at this point is that whoever put the Doctor in spooky jail is trying to show him how much his life resembles a Nelly Furtado song.
But anyway, a secret door randomly opens revealing a spiral staircase that leads to the top of the central tower. He looks at the stars and is like “These stars are not in the right position! I’m starting to feel like something bad is happening and I’m dumb for not figuring it out!”
Later he walks down a corridor and does a double take and goes down a hallway and finds a door with “12” on it. But when he opens it there’s a wall on the other side, so I guess he’s going to need to face the creature again and get it to rotate! He’s not super into that idea though because he doesn’t want to play by the rules of whoever made up this fun game for him and some of his secrets are not safe for public consumption.
He goes back up to the top of the tower and when the creature catches him he confesses that he knows that the half-Dalek-half-Time-Lord hybrid from the Time Lord legends (which we first heard about back in the underwhelming two-part season premiere) is real and who it is and where it is and that he’s scared of it. The walls move and he goes back to Door #12.
Inside there’s a wall made of what looks like ice but according to the Doctor is some super hard substance that’s like diamonds times a million. And at this point I want to revise my previous statement and say that this is less like the Ocarina of Time Forest Temple and more like the Majora’s Mask Snowhead Temple.
On the other side of the superdiamond wall he can see the TARDIS, and he knows that to get through he has to make one last confession: telling the creature about the Hybrid. He goes into his mental TARDIS and throws a temper tantrum about how it’s always his responsibility to take care of things and win against the bad guys and his BFF is dead so why can’t he just spill the T and lose this one so he can go home and eat a pint of ice cream and cry?!?!? But imaginary Clara stops writing on the chalkboard and turns around and tells him to pick his sorry ass up and take care of business. It’s very sad! I’m still very sad that she’s dead! Ugh!
So the Doctor starts punching the superdiamond wall and the creature approaches and he’s like “Guess what, the secret of the Hybrid is 2 hot 2 handle and I’m never telling.” The creature puts its creepy hands on his face and he screams.
JK! The creepy hands-on-face maneuver was apparently fatal, but it takes Time Lords a long-ass time to die so the Doctor crawls up to the pneumatic tube room to plug himself into the teleporter and electrocutes himself to boot up the copy of his original just-came-from-Clara’s-death self inside the tube and start the whole process again. Because SURPRISE! He’s been in this prison for 7,000 years and keeps doing the same thing over and over and all the skulls are his! He realizes that the “bird” message is him telling himself to remember this parable about a bird sharpening its beak on a diamond mountain until the mountain is gone, so every time he makes it to room 12 he ends up repeatedly punching the superdiamond wall until the creature gets him and he has to start over and eventually after literally billions of years of this bullshit he finally breaks through to the other side.
He emerges out onto some kind of deserty planet and finds that this whole time he’s been inside his confession dial (which Arya made him fork over last week). A little boy comes up and the Doctor is like “Hey kid, go find somebody important and tell them that I’m back and I know what shit they pulled with me and I’m mad as hell!” Because guess what? He’s back on GALLIFREY! And P.S. There’s no such thing as a half-Dalek and HE IS THE HYBRID!