“Knock Knock” is episode four of season ten of the new Doctor Who.
At the end of the previous episode, “Thin Ice”, Nardole was at the mysterious vault – and something was knocking on the other side of it. So, this episode opens with someone knocking – no surprise – but it’s with an ordinary knocker on an ordinary door. The door is answered by Bill, who is going to be the new flatmate of the people knocking. They are students looking for a new house to live in, but they aren’t having much luck finding anywhere for a price they can afford. Then an older gentlemen offers them a really, really, really large mansion for them to live in, very cheaply. So they accept – all they have to do is sign a contract. This already seems like it’s going to be a mistake.
That night, a young man is wandering around the place in dark, with creaky floors, before he puts on some vinyl. The floors continue creaking, as if there’s someone else there. Then he moves out of sight, says no multiple times followed by some nasty rending sounds and a scream. There was probably a reason for the mansion to be cheap.
Bill has piled her stuff into a pile for moving, and the Doctor materialises the TARDIS around it. He’s helping her move and Bill suggests that he hires the TARDIS as a removal service. After which the Doctor tells her he is a Time Lord, and there’s a conversation about what they are – and the topic of regeneration comes up before being quickly skipped over. When the Doctor sees the house, he seems a bit curious and helps Bill move in. Even though she asks him not to. Being a lecturer at the university, the students all seem to recognise them. As Bill is moving in to her room, she hears creaking. Having seen a few creatures already, she’s a bit nervous about this.
It’s a dark and stormy night and the students are together in a sitting room when they hear noises from the kitchen. When they go to investigate, they find – the Doctor. Who is examining the house very carefully. The Doctor suggests that they all move out. The gentleman who rented the house arrives and, when asked about how you get into the tower, he replies, rather insistently, that you don’t. It’s excluded from the rental. Something is definitely off with him – especially when he disappears seconds after leaving. The house is still making weird noises. Bill is still trying to get the Doctor to leave, but he isn’t going. She is sure there isn’t anything going on. He isn’t. Then another student goes into his room, closes the door and there’s screaming. Then something starts knocking from inside the room. Then the walls. Then they are all completely sealed inside the house. Which has sealed itself up. Then another student disappears.
Is there something in the walls or is the house eating people? And what’s the role of the creepy landlord in this?
The knocking wasn’t to do with the vault, but there’s more regarding it at the end of the episode.