Doctor: Peter Capaldi (Twelfth Doctor)
Companion: Jenna Coleman (Clara Oswald)
Keeley Hawes – Ms Delphox/Madame Karabraxos
Jonathan Bailey – Psi
Pippa Bennett-Warner – Saibra
Trevor Sellers – Mr Porrima
Ross Mullan – The Teller
Mark Ebulue – Guard
Junior Laniyan – Suited customer
Samuel Anderson – Danny Pink (uncredited)
Directed by Douglas Mackinnon
Written by Stephen Thompson
Script editor David P Davis
Produced by Peter Bennett
Executive producer(s) Steven Moffat
Incidental music composer Murray Gold
Series Series 8
Length 45 minutes
Originally broadcast 20 September 2014
While at Clara's flat, the Doctor answers the TARDIS's phone; both are surprised to find themselves on an alien planet in a room with two others: Psi, a hacker with an augmented brain, and Saibra, a mutant that can shapeshift into any form by touch. They all suffer short-term amnesia. A recording includes messages from each agreeing to a short-term memory wipe, before giving instructions from "The Architect" to break into the Bank of Karabraxos and steal three items from its vault.
Saibra and Psi help them gain access to the Bank. It is secured by Ms. Delphox using a highly-telepathic alien called the Teller to detect those with criminal intent and destroy their brains; the Doctor believes the memory wipes were needed to avoid being caught. Within, they find six devices left by the Architect that appear to be disintegrators, to be used if they are caught by the Teller to avoid a painful long death. Both Saibra and Psi sacrifice themselves with these devices when they encounter the Teller, allowing the Doctor and Clara to reach the vault doors.
The doors appear impossible to open, but then a large solar flare strikes the planet's surface, triggering an automatic unlocking sequence; the Doctor realises this was a "time heist". They recover two items, a serum to stabilize Saibra's DNA, and a device to restore Psi's long-term memories lost from augmentation. They are caught by Delphox and two guards while trying to find the Karabraxos personal vault. She is called away, and the guards reveal themselves as Saibra and Psi; the devices are actually short-range teleports to a ship waiting in orbit. The two insist they leave as the solar flare threatens to destroy the Bank, but the Doctor wants to uncover the third item.
In the personal vault they meet Madame Karabraxos, who is hastily packing valuables and evacuating. The Doctor realises Delphox is her clone, and on hearing this, she orders her clone's destruction, and directs the Teller to the vault. Before Karabraxos departs, the Doctor, sensing her unease, gives her the phone number to the TARDIS to use when she has a moment of regret.
When the Teller arrives, the Doctor willing allows it to scan his mind, restoring his short-term memory. The call to the TARDIS was from a dying Karabraxos, regreting something she left in the vault. The Doctor became the Architect of the time heist to assemble Saibra and Psi and plant the devices to get them to this point. Freed from the Teller's scan, the Doctor shows them why they had six of the teleportation devices: that Karabraxos wanted him to rescue the Teller's mate that she had locked up to force the Teller's cooperation.
They evacuate the Bank in time, and the Doctor leaves the Teller and its mate on an habitable but unpopulated planet to live out in peace. The four enjoy a celebratory meal before the Doctor returns them to their proper times and worlds.