I like the fact that this episode is a mystery from the beginning. The Doctor, Clara and two other people are sitting at a round table with a briefcase and several worms on the table. A woman introduces herself as Sabra. The gentleman sitting next to her says his name is Sy. He is dressed in black, but his head is somewhat half shaven with a mechanical device on his temple. The Doctor recognizes the worms known as memory worms. A voice recording of their own voices said that they use the worms to wipe their memory with consent. Then a video screen appears and a dark figure is sitting in front of it. He says that they are on a planet that houses a highly sophisticated bank for the super rich and that anyone who breaches their security, will be immediately disintegrated. The dark figure calls himself the Architect, and that he wants them to break into the bank and steal something. And if they don’t help him, he will allow security to take them. They all agree to help him, so the Architect helps them to escape.
Walking into the lobby of the bank, they are impressed with the structure of it. They witness a customer being detained by security and the Head of Security, Ms. Delfox. A creature, known as the Teller, with strange eyes stand in front of the customer, and Ms.Delfox accuses him of the criminal thoughts and that is not allowed. The Teller then uses some sort of telepathic abilities to probe the man’s brains, and by doing so, it would siphon all his memories from him. It puts a huge dent in his head. He is taken away. The Doctor and his accomplices walk away into another room. There they find a safety deposit box. They find a way to open the box and find an explosive device. 
The Doctor reads the schematics of the bank finds out that they have to go the lowest level of the bank. They use the device to blow a hole in the floor. They go through the hole and down through the inner walls of the bank. They find a suitcase with several strange metallic devices. The Doctor takes them, not knowing what they are, but he is pretty sure the Architect put it there. They split up, the Doctor with Sabra, and Clara with Sy. The Doctor and Sabra head towards the tunnels that lead to the banks corridors. Sy uses his computer device in his head to connect with the interface. Talking with Sy, Clara gets to learn that Sy is a prisoner interrogator and hacker. In order to make room for any programs in his head, he had to dump a lot of his memories, specifically his friends and family. Clara found that to be sad and scary. The Doctor and Sabra are met with the Teller in the corridor. By Ms. Delfox orders, the Teller was sent down here to track the unwanted guests and dispose of them. Sabra is caught in the Teller’s mind grip. She takes the strange device from the suitcase, hoping it would help free her of the Teller. It did, but with a cost, her life. Clara and Sy, who happen to meet up with the Doctor witness her being disintegrated, grieve for her, but the Doctor doesn’t. He has a job to do, no time for grieving. That doesn’t sit well with Sy. The Doctor doesn’t care.
They reach the vault, but it is armed with a multiple atomic locks. Sy uses his computerized brain to try to unlock the locks. The Teller finds them and the Doctor and Clara attempt to create a diversion by steering the Teller away from Sy. But before they run, Sy asks for one those devices from the Doctor. He agrees. The Teller finds Clara and starts probing her mind. Hearing her cries, Sy decides to draw the Teller toward himself. He then opens his mind and the Teller goes towards him. He is able to unlock all but one the locks before he sacrifices himself. Clara reunites with Doctor at the vault only to find the vault is still locked. Outside a solar storm hits the planet. It puts the banks system into a shutdown mode. The Doctor is starting to piece together what is happening. The Architect knew about the storm, because he’s a time traveler and placed the group in a time just before the storm, that way when the storm hit it the bank it would allow the group to go into the vault unsecured. They both walk in. 
Clara is holding a piece of paper that she had along with three sets of numbers and letters. She realizes that they are safety deposit numbers for them to look for. They find those boxes and the contents appear to be things that Sy, and Sabra needed to cure themselves. The third line on the paper says “PV”. Just when they try to find PV, the Teller finds them. They are brought to another room filled with artifacts and precious things. A woman that looks exactly like Ms. Delfox is sitting behind a desk. She is the director of this bank, and that Ms. Delfox is a clone. Disappointed by the clone’s competence she has her destroyed. The Doctor realizes how the Architect is connected to this. Watching the director’s behavior toward to clone, he concludes that the Architect is him but in the future. But the puzzle is still not solved, why here? Why now? The director tells security to kill the Doctor and Clara. The storm is already ripping the planet apart and damaging the bank. The director finally decides that it is time for her to leave, but before she leaves the Doctor warns her that she will die an old woman with lots of regrets of what she has done in her life, and not to with any regrets. The guards then grab the Doctor and Clara, and they think it’s over. Just then one of the guards changes before their eyes. It is Sabra, and then Sy appears behind a guards mask also. Apparently they were not destroyed but transported to a different place. The Doctor then gives the contents of the box to Sabra and Sy, knowing it will save their lives. But the Doctor is still puzzled as to why he is here. He realizes the only way to find out is to have the Teller read his mind and memories. It probably knows the missing time that the Doctor needed to solve this mystery. Apparently, the Doctor got a call from the director on her death bed, claiming that she wants to die with a clean slate. She needed the Doctor to do one thing for her, he agrees. This whole bank heist, the memory wipe, and the Architect, was all him. All this was a strategy to fool the bank security system to help the Teller find his mate. The Teller then realized that his mate is in a vault locked up in chains. They find the vault and free the Teller’s mate. The Doctor says that this was not a bank heist after all, but a rescue.
It reminded me of the old episodes where the TARDIS takes them to places that weren’t on their flight plan and yet they investigate the place anyway, because it is an adventure. There wasn’t any story arc or plotlines that connect to anything. It was just a great stand alone space adventure. It was exciting, and fun to watch.
