The Phone Call

The Doctor tries to convince Clara to come with him for a day sightseeing via the TARDIS but she is about to go on a date with fellow school teacher, Danny Pink. Just as she is about to leave, they hear the TARDIS phone ringing. They are both curious as they know that very few beings in the universe know The Doctor's phone number.

As The Doctor goes to answer the phone, the two of them suddenly find themselves in a strange chamber suffering from memory loss, with the likely culprit - a Memory Worm - wiggling around on the table. They are not alone as they are with two others - Psi, a hacker with an augmented brain, who had previously lost his memories when he was convicted as a criminal, and Saibra, a humanoid with the ability to shapeshift who seeks to become more human and who has also lost her memory.

A briefcase on the table then opens to reveal plans by a person, who introduces himself as 'The Architect'. He instructs them to rob the Bank of Karabraxos - the most impregnable bank vault in the universe with numerous levels of security. As guards are about to break into the room the group takes tools, provided in the cases, and flee from the room.

Inside the Bank

They work their way back to the main floor of the vault, with Saibra using the identity of a customer to gain them access to the bank. There they witness another customer, accused by the bank's head of security, Ms. Delphox, of planning to steal from the bank. He has his brain scanned and then turned to 'soup' by The Teller, an alien with powerful psychic abilities that is said to be the last of its kind.

Despite this warning, of what will happen to them if they are caught, The Doctor, Clara, Psi, and Saibra continue to follow The Architect's plan, finding more cases with useful items left by The Architect as they get closer to the main vaults. At one point, they collect six devices whose purpose The Doctor claims he does not know.

The Teller

Part of the plan requires them to pass through the cage where The Teller is kept in near-hibernation, but the creature picks up on Clara's brainwaves. The Doctor is able to help Clara break out of The Teller's scan and so enable the group to flee the room - except for Saibra who then becomes caught in The Teller's scan. Unable to free her The Doctor gives Saibra one of the devices, telling her it is an atomic disintegrator and so a more humane way to die than The Teller's brain scan. Realising she has no choice she activates the device and disappears.

As the three continue to the main vaults, they soon realise that Ms. Delphox has released The Teller to chase them down. Psi though stays behind, to help cover their tracks and open the vault. He too opts to use one of the disintegrators when he is caught by The Teller when he sacrifices himself to save Clara who again gets caught by The Teller's scan.

The Doctor and Clara eventually reach the main vaults just as a solar storm begins to strike the surface of the planet. The Doctor realises that they are involved in not just a bank heist, but a time heist, and that The Architect is from the future and he planned to bring them to the vault at this moment when the storm's activity would cause the main vault to automatically open. Inside they locate two safe boxes indicated by The Architect, one containing a neophyte circuit that would have restored Psi's deleted memories, and the other a gene suppressant that would have stabilised Saibra's uncontrollable shapechanging abilities. If only they had not been killed...

Ms Delphox

However, as they look for the final safe box location (in the Private Vault), they are caught and taken to Ms. Delphox's office. She takes the stolen goods and leaves, to put The Teller back into hibernation to protect him from the worsening solar storm, ordering her guards to kill them. The Doctor and Clara though are surprised when the guards turn out to be Saibra and Psi - the disintegrators were really teleporters. The Doctor gives the two of them the items from the vault as their payment, but realises they still need to find the Private Vault. Psi leads them into the depths of the bank as the storm intensifies on the surface.

Inside the Private Vault, they find that it is in fact the quarters of Madame Karabraxos, who is surrounded by treasures from around the galaxy. The Doctor realises that Ms. Delphox is just a clone of Madame Karabraxos and she has no problem sending her clone to be incinerated for failure. At this point inspiration strikes The Doctor, and he writes the number to the TARDIS telephone, and that he is a time traveller, on a piece of paper and gives it to Madame Karabraxos, who is hastily packing her treasures before the storm wipes out the bank. As she departs from the vault The Doctor reminds her to give him a call if she has any regrets. Shortly after she leaves, The Teller arrives and The Doctor convinces the alien to scan his mind to find the memories that were blocked by the memory worm.

In a flashback, an elderly and dying Madame Karabraxos - now no longer the richest person in the universe - calls The Doctor on the TARDIS's phone while it is in Clara's flat, and tells him of her regret. The Doctor is then shown preparing all the elements of the time heist, revealing that he himself was The Architect. Because much of the bank's security was based on sensing a criminal's guilt, wiping the short-term memories of The Architect's group would reduce their chances of being caught. The ultimate goal was to bring The Teller, who was telepathically linked to Madame Karabraxos, to the Private Vault after she left, so as to allow him to unlock a combination safe. Inside, they find another alien of the same species as The Teller, chained within the safe but otherwise unharmed; The Doctor then points out that they have the six teleport devices allowing them all to escape the bank before it is destroyed by the solar storm.

Escaping from the bank before it is destroyed The Doctor takes the two aliens to a habitable planet to live out their lives in peace. He then returns Saibra and Psi to their homeworlds before finally piloting the TARDIS to return to Clara's flat moments after they left to allow Clara to continue on her date with Danny Pink. Right after Clara departs, The Doctor declares with a smug grin 'Ha! Robbing a bank! Robbing a whole bank. Beat that for a date!'.