Story 269: Knock Knock

In which Bill Potts and some of her university friends - Shireen, Harry, Paul, Felicity and Pavel - decide to enter into a flat share together. After a number of properties prove to be too expensive or badly sited, they are met by a man who tells them that he knows of a place which is very reasonable in rent, as he is its landlord. They are taken to a large suburban house - 11 Cardinal Road, Bristol - which seems ideal, though they are suspicious as to why the rent is so cheap. The building has a tower room, which the landlord specifies is not included in their tenancy and is out of bounds.

Pavel moves in first, spending his first night on his own. He sets up his record player, as he is a fan of classical music. He notices a strange movement on the surface of the bedroom's wood panelling - which is caused by large cockroach-like insects. Pavel is dragged into the wall.

The Doctor helps Bill move in the following day, carrying her belongings in the TARDIS. Her friends believe him to be her grandfather. They hear Pavel's record player repeating the same piece over and over again, but just assume this is deliberate.

Everyone gathers in the lounge, apart from Pavel, and they hear loud noises coming from the kitchen. there is no-one there. Other bangs sound from the walls and ceiling. They also discover that they cannot get any mobile signal, and there is no telephone landline present. The landlord appears unannounced, having apparently let himself in. He has a curious habit of using a tuning fork to test the wooden walls. 

Bill is surprised to come across the Doctor, still in the house and looking around. He points out that the building lacks central heating and the electrical wiring is all obsolete.

The flatmates decide to make for bed, whilst the Doctor remains downstairs with Felicity and a curious Harry. Shireen and Bill hear a cry coming from Paul's room, but there is no response when they go to check on him.

The Doctor discovers that the front door will not open. Felicity panics and clambers out of the kitchen window. Leaning against a tree in the garden, she screams as it pulls her towards it.

Bill and Shireen decide to enter Pavel's room when it becomes clear that he is not changing his record. They are horrified to find him partially absorbed into the wooden panelling of the wall. The landlord suddenly appears and removes the stylus - and Pavel is fully absorbed. The young women run off, and discover a hidden entrance into the tower.

Downstairs, the Doctor and Harry descend to the basement. They discover a number of boxes containing someone's belongings. Examining these, they find that they belong to different groups of young people, spanning many years. each box represents a group of people 20 years apart. The Doctor is convinced that something is living in the wood, which he decides to call Dryads after the classical wood nymphs of myth. They see a mass of these appear - giant cockroach-like creatures earlier seen by Pavel. When Harry runs up the wooden steps, he is overwhelmed by them - apparently devoured. The landlord seems to be able to control them, and the Doctor realises he is using sonic vibrations to do so.

Bill and Shireen discover a bedroom at the top of the tower, and within is the landlord's daughter Eliza. She has been turned to wood. The Dryads attack and consume Shireen. Bill is saved by the intervention of the Doctor, who is followed by the landlord.

The Dryads have been keeping Eliza alive, and the Doctor realises that she is not the landlord's daughter but his mother. As a little boy he had brought some of the insects to show his ailing mother, and they had saved her by transforming her into wood. The creatures need to be fed every 20 years, and the landlord has lured groups of people into the house with the promise of cheap rent.

A student party is going on in a nearby park, and Eliza comes to realise the nature of her solitary existence. She can no longer allow people to die just to keep her alive in this state. She summons the Dryads and they consume her and her son.

The building begins to collapse.

All of Bill's friends who had been captured by the Dryads are freed unharmed, and everyone flees as the house disintegrates.

Later, back at the university, the Doctor and Nardole listen as piano music can be heard coming from the vault... 

Knock Knock was written by Mike Bartlett, and was first broadcast on Saturday 6th May, 2017.

This is Bartlett's only Doctor Who story to date. An award-winning playwright, he is best known for the series Doctor Foster, which starred Suranne Jones, as well as the play King Charles III. This was adapted for television in 2017, starring the late Tim Piggott-Smith as the monarch.

Bartlett decided to do a "haunted house" style story, making use of the idea of creaking floorboards as a scare factor. Steven Moffat was always happy to see everyday things which a child might encounter transformed into a thing of fear.

He recalled the problems he had personally experienced as a student in Leeds trying to find affordable accommodation, and the housing crisis had become more pronounced in 2017.

Another inspiration was the visit to his parents of a man dressed entirely in shades of brown, which he recalled from childhood.

Because of the important role which sound had to play in this episode, it was made available with a special binaural 360 degree soundtrack on the BBC i-player.

The guest cast is headed by David Suchet, who is world famous for his role as Hercules Poirot in the ITV series. He has played the Belgian detective in adaptations of every one of his novels and short stories. Since completing the run with Poirot's Last Case, Suchet has mostly acted on stage or fronted documentary series on TV. Suchet was very happy to help promote his appearance, claiming it was one of his ambitions to feature in the series.

Eliza is Mariah Gale, who played Ophelia to David Tennant's Hamlet in 2009. An RSC member, her work is almost entirely stage-based, though she did also appear on TV in the third season of Broadchurch. 

Bill's friend Shireen is played by Mandeep Dhillon, and Harry is Colin Ryan.

Paul is played by Ben Presley, Felicity by Alice Hewkin, and Pavel by Bart Suavek. 

Presley is another actor who has played opposite Tennant - in the comedy drama What We Did On Our Holiday. Hewkin featured in Solo: A Star Wars Story.

As far as the series story arc goes, the vault is seen at the close of the episode. Whoever is inside can be heard playing the piano, and we learn that it is dimensionally transcendental.

Overall, a nice "haunted house" story. The wooden woman makes for a very creepy-looking character, although she turns out to be a sympathetic figure.

Things you might like to know:

• Bill's friend Harry was supposed to be the grandson of ex-UNIT member Harry Sullivan. Young Harry was studying medicine like his grandfather. This was dropped late in the day as it was felt to be too obscure a reference.
• The house used for the location work was the same one which had been used as "Wester Drumlins" in Blink. Shireen describes the house as having a Scooby-Doo vibe - which is exactly what Larry said of "Wester Drumlins" in the Weeping Angel story.
• The exact nature of the Dryads is left open. Are they terrestrial cryptozoological creatures, or alien in origin? They don't even have a name - the Doctor titling them after the wood nymphs of Greek mythology.