The Doctor arrives in the TARDIS in Clara's flat and tries to convince her to come sightsee with him as she prepares for a date with Danny Pink. Suddenly, the TARDIS phone rings, and when the Doctor goes to answer it, the two find themselves in a strange room on an alien planet, with no memory of how they got there. Two others, both with short-term amnesia, are there: Psi, a hacker with an augmented brain who has sacrificed his personal memories for the cybernetic implants, and Saibra, a mutant humanoid with the ability to shapeshift into another by touching them, a talent which she considers a curse as it prevents her from getting emotionally close. They find a recording of themselves agreeing to a short-term memory wipe and instructions from an unknown entity known as "The Architect" instructing them to break into the Bank of Karabraxos and steal very specific items from its vault. They flee the room as guards approach.

Saibra's abilities allow them to enter the bank as customers. They observe the bank's head of security, Ms. Delphox, employ the bank's primary security measure, a highly telepathic alien creature known as the Teller who can sense criminal thoughts, lock that person into place as it scans their mind, and then destroy their brain. The Doctor surmises that the memory wipe was to help protect them from the Teller. The group continues deeper into the bank, finding more messages and items left by the Architect to help them, including, at one point, six handheld devices that the Doctor believes are personal disintegration units. As they proceed deeper, they are forced to pass near the cage where the Teller is kept. Clara is inadvertently caught in the Teller's scan, but Saibra pushes her out of the way, and becomes the target of the scan. The Doctor implores her to use the disintegrator, as it would be a far less painful fate. The others can only watch as her body disappears. Ms. Delphox later releases the Teller to track them down in the corridors near the vault. When the Teller is close to detecting Clara, Psi purposely thinks of his past criminal acts, drawing the Teller to him, and then uses the disintegrator as Saibra had done.

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