Knock Knock

"Knock Knock" is the fourth episode of the tenth series of the British science fiction television series Doctor Who. It was written by Mike Bartlett and was broadcast on 6 May 2017 on BBC One. "Knock Knock" received mixed to positive reviews from critics, receiving criticism regarding the strength of the writing, but praise on the quality of the performances in the story, particularly Suchet's. Bill Potts (Pearl Mackie) and her friends rent a house to live in after a recommendation from its landlord, played by guest star David Suchet, but the Doctor (Peter Capaldi) notices something wrong with the house when the floor and the walls creak and creatures come crawling out of the wood. Synopsis Bill and five students (Shireen, Pavel, Harry, Felicity and Paul), seeking to room together, take an offer by an elderly Landlord for a large mansion at very low cost, as long as they do not enter the tower. Bill gets the Twelfth Doctor to help with her move. The Doctor inserts himself among Bill's friends by posing as her grandfather, to Bill's consternation, and is troubled by the numerous noises the house makes. Later, the Landlord mysteriously appears, ostensibly to check on the students. Suspicious of him, the Doctor tests him by asking who the Prime Minister is and names several, including Harriet Jones. The Landlord, however, evades the question and leaves. As night falls, the knocking noises grow, and Bill's friends start to disappear. All the exits from the house are sealed tight, preventing any of them from leaving and separating the remaining ones. Bill and Shireen see Pavel half-absorbed in the wall, and the Landlord appears, striking a tuning fork which causes Pavel to disappear completely. The Doctor discovers the house's woodwork infested with insect-like creatures he calls Dryads. They are responsible for drawing the others into the woodwork prior to consuming them. The Doctor and Harry soon find evidence that every twenty years, a new set of students have been brought to the house to feed the Dryads. The Landlord arrives and admits that he needs the Dryads to keep his daughter Eliza alive in the tower.