Knock Knock (Doctor Who)

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.

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.

Suspicious of him, the Doctor tests him by asking who the Prime Minister is and names several, including Harriet Jones.

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.

When they heard a high-pitched sound from her music box, they awoke and started turning Eliza to wood to stave off her illness.

This is a reference to many previous episodes in which Time Lords had been seen wearing large collars with their robes, which were introduced in The Deadly Assassin (1976), and had most recently been seen in "Hell Bent" (2015).

[2] David Suchet stated he "completely freaked" when he realized on the third day of filming that his family had rented exactly the same house the Christmas before for the holidays.

"[22] 88% of 17 critics gave the episode a positive review on Rotten Tomatoes, and the website's critical summary reads, "A bit of narrative weakness aside, 'Knock Knock' is a wonderful mix of nostalgia, horror, humor, and monsters that culminates into[sic] a powerful and emotionally complex episode.

[17] Scott Collura of IGN gave the episode an 8.7/10, complimenting the dynamic between the Doctor and Bill, especially their "father or grandfather" relationship.

He stated that the series thus far had been light on alien menaces and the explanations for them, and that the mood created was effective, but it did little else for the episode.

Ruediger also mentioned the inability to "overcome the glaring plot holes and weird inconsistencies in the script", such as the failure to release the previous tenants along with Bill and her friends, and the number of questions the episode left unanswered.