Clara is in her Zygon pod. Clara wakes from a dream. She sees the numbers on her clock inverted at first. They correct, and she walks into her bathroom. Her toothpaste is labelled “THIS IS TOOTHPASTE,” and comes out of the tube black. She hears something on the television. She walks into the living room and hears what the Doctor told her Zygon imposter at the end of the previous episode. She tries to leave her apartment, but there’s no exit. Clara’s eyes flicker in the Zygon pod. She reads a paper. Its mostly gibberish, but she finds messages. “It’s your decision Doctor.” “Truth or Consequences.” Clara is able to exhibit some control over her double. She knocks the rocket off course. She stops her double from pulling the trigger a second time…at least for a moment, before she fires and blows up the Doctor’s plane.
The Zygon extremist insiginia is all over London. They’re sweeping charged ashes off the street. A harried man goes into his apartment, but Bonnie – Clara’s double – follows him. She says she’s going to set up free. Bonnie says the man is going to be the first to make the humans see. The man begins to forcefully change into a Zygon form. He cries for help, but no one aids him. Bonnie records him running through the street in Zygon form. She makes a call and says she’s going to retrieve the Osgood box.
Still in her pod, the images of the Doctor’s plane exploding plays on Clara’s TV. She’s able to pause the image, and see two parachutes drifting away from the explosion
The Doctor and Osgood land on a beach. Osgood wonders why the Zygon hesitated. Clara continues to exert some control over her double, dialing on her phone. She sends a message to the Doctor that reads “I’m awake.” The Doctor doesn’t understand, but Osgood explains.
Bonnie goes into Osgood’s office. She takes a moment to examine (admire?) herself in a mirror. She then opens a safe and takes out a laptop. She watches a video of Osgoods explaining that the Osgood box isn’t really there. Enraged, Bonnie destroys the laptop.
The Doctor approaches some police officers in a car, flashing his psychic paper. They just silently stare at him. He notices something is off, and walks away. Osgood calls Bonnie on Clara’s phone. She answers. They argue a bit. Bonnie winks. Doctor calls her out on the strange behavior, but she insists she didn’t wink. The Doctor realizes Clara is communicate through Morse code in wink form. He gets info on where the pods are. The Doctor tells her not to reveal anything about the Osgood box. The Doctor an Osgood leave in a van. Osgood tracks Bonnie’s phone, and sees the video online of the Zygon Bonnie forced to transform.
Bonnie goes to Clara’s pod and communicates with her through the TV. Bonnie threatens Clara, but Clara calls her bluff. Clara plans to lie, but Bonnie reveals their heartbeats are linked. Lying won’t work.
The Doctor and Osgood arrive in London. They track Bonnie’s signal. The entire a building with a stench, and see two piles of ash.
Bonnie interrogates Clara. She asks about the Osgood box. She points her to the Black Archive under the Tower of London. She says the Doctor, Osgood, and herself have access to the box. Bonnie tells her to give over her access, but Clara says she can’t. Clara tells her there is a button inside the box that unmasks every Zygon on the planet for an hour. Bonnie asks why it’s called the Osgood box. Clara doesn’t tell her, and says once she gets to the Black Archive she’ll understand and want to talk again.
The Doctor and Osgood continue through the building. They the forcibly transformed Zygon and chase after him. He explains what happened. He zaps the Doctor and runs.
“Kate” arrives and London and reports to Bonnie. Bonnie orders her to duplicate and kill the Doctor.
The Doctor and Osgood try to reach out to the Zygon. The Zygon laments his fate, saying he was happy how he was and just wanted to live. The Zygon fries himself, rather than allowing Truth or Consequences to take him. Afterwards, “Kate” finds the Doctor and Osgood and offer to take them to Clara.
Bonnie arrives as the Black Archive and lets herself in. Meanwhile, “Kate” leads the Doctor and Osgood to the pods, and Osgood realizes they’re Zygons. Bonnie finds the Osgood box. She calls “Kate” and tells her they call it an Osgood box because there are two of them. The Doctor tells her one box reveals the Zygons, and the other destroys them. Inside the boxes, each has a button for Trutha and another for Consequences. The Zygons move to capture the Doctor, when “Kate” reveals herself to actually be Kate, and kills them both.
The Doctor arrives at the Black Archive. He offers to take both the boxes away and forget this ever happened. Bonnie refuses. Kate takes position at another. Kate’s box will either kill the Zygons, or detonate a nuke under Lodnon. Bonnie’s will either unmask the Zygons, or kill them. The Doctor tries to see if Bonnie has thought all this though, reminding her that the wheel keeps turning and that she could break the cycle. He then turns on Kate, explaining that the boxes are a scale model of every war. Bonnie says the Doctor doesn’t understand. The Doctor recalls the Time War, the things he did ad the pain it eft him with. Kate closes her box. Bonnie realizes that the boxes have nothing in them, just buttons. She pulls her hand away. Kate says they can’t forget the boxes are empty now. The Doctor says that’s what she said the last 15 times, and wipes her memory again. He leaves Bonnie’s memories, and says he was in the same position as her not long ago. Then he let Clara get in his head.
Bonnie reinstates the ceasefire.
The Doctor shows Osgood the TARDIS. He invites her to come, but Osgood says she tinks she needs to stay. The Doctor asks for a moment alone with Osgood. Clara hugs Osgood, and enters the TARDIS. The Doctor tries again to get Osgood to tell him which one she is. She says she’ll answer on the day that the answer doesn’t matter. A second Osgood appears. Its Bonnie’s new form.