Reviewed by Ryan Monty.

(This review continues spoilers. Read on if that doesn’t bother you!)

After heroically saving an imprisoned giant fish beneath the frozen Thames last time out, The Doctor and Bill are treading on even more thin ice (sorry) when Bill moves into new digs with her university friends, into a house owned by an ever-so slightly creepy Landlord, played by Poirot himself David Suchet. Bill’s hoping this is just a step back to the ordinary after moving puddles, weird robots and giant fish- but of course this is Doctor Who so it’s absolutely the opposite of that, because this Landlord is hiding secrets. Following from three breathless, back to back adventures, Bill’s getting back in touch with the ordinary, finding a house to live in with her friend Shireen and her friends. It may sound like relatively easy going, but in this opening segment, Bill and co. must face a threat worse than any Dalek, Cyberman or Kandyman could ever pose- finding affordable student housing. Truly horrifying.

This pre-titles scene is just full of energy and character. Set to the tune of “Weird People” by Little Mix, Bill and friends searching for houses in vain is warm and down to earth, giving the show another boost of vibrant realism to it. It’s little scenes missing like these that is arguably why many soured-on Clara Oswald, her home life never quite seeming real as presented. Bill however is very much of our world, with her housemates too being a varied delight of personalities and multiculturalism. When options seem to be running out, in steps Suchet’s Landlord, and they think they’ve found themselves the perfect place for cheap. After a terrific sequence with The Doctor helping Bill move in, and Bill explaining he’s her grandad (and not father, despite The Doctor’s protestations), she’s all settled in. However, the wood creaks and there’s a nasty draught setting in the old-fashioned house. The only problem being, there isn’t any wind. There’s creepy-crawlies in the wood, and there’s something hidden away in the tower.

The most heavily promoted aspect of this episode prior to broadcast was that online viewers could indulge in a special version of the episode, with a binaural sound mix. This is known as 3D sound, where the sound mix for this episode has been mixed in a way which tricks your ears into thinking that sounds-say, knocks- are emanating from different areas, whether up, down, or in front of you. So about perfect for a story set in a not at all creepy house, really! Even just watching normally on your telly, the sound work is still highly effective. The nature of this episode is of the haunted house variety, and so as you’d expect atmosphere and sound work are vital parts of it. And the episode builds at a good pace, allowing you to be sucked into the creeping sense of dread building. Yes, this very much has all the trappings of the classic haunted house stories, but the intrigue is built well- Bill is initially convinced nothing is wrong, trying to keep The Doctor out of it- and then doors start not being doors, the floorboards creak and the residents start disappearing.

Despite the episode having the furnishings of a haunted house horror, refreshingly the main cast aren’t, for once, total lumps of wood (sorry again), and make what would be the normal decisions made in such a situation. When The Doctor is conducting his investigations into the house and things start going south, one of Bill’s housemates instantly realises that events are not normal and that sticking with The Doctor is the smart idea. Hearing the pitch of the episode you’d be worried that the student characters would be portrayed as complete idiots, but thankfully they make (mostly) all the decisions you yourself would probably make and you aren’t wishing them all a death after stupid things they do (which is nice). Even mistakes they do make are excusable when you’ve got a house that isn’t right at all and a sinister landlord appearing spookily from nowhere.

Bringing David Suchet on board as the villain was an inspired choice. With a performance that brings at the same time fear and pathos, his Landlord is a great addition to the gallery of Who villainy (and sympathy). He chills throughout the story before you discover his origin, popping up at random intervals almost magically, skulking in the background throughout as an ever-present threat, an old man putting on a nice face to hide his cold reality- and Suchet lets you see deep into that, his façade dropping almost instantly whenever questioned about the tower at the top of the house. He’s especially blasé when seeing to Pavel, who’s half trapped in the wood, calling it a “mercy”. In the closing stages of the episode you do discover his true nature, and while he still clearly unremorseful for the deaths he caused, you can clearly see just how insane and trapped the Landlord has become. A child still, in an adult’s body, driven only by the love of his mother. That’s the driving theme for the episode- motherhood.

Early in the episode, when Bill is exploring her room (can I say how much I love Bill’s theme already? Because I really, really do!) she takes out a framed picture of her mother, having a touching “conversation” with her. And during the final confrontation of The Doctor, Bill, the Landlord and the mother he’s gone to such lengths to save, the Landlord bellows “If you could save the one who brought you into this world, wouldn’t you?”. The camera cuts immediately to Bill’s reaction, and she understands. The Doctor is silent, too, because he knows as well, and we the audience too. Would you? It’s this tricky question that draws the sympathy for the Landlord, because he is so clearly still mentally a distressed child, so much so that he’s allowed her to become what she is just to save her. This final emotional climax to the episode is played beautifully by David Suchet and Mariah Gale as his mother Eliza, leading to a moment when Eliza sees the outside world, and fireworks, wanting only for her son to lead his own life, but he is loyal to her till the end, and I felt rather sad for him.

Before the episode reaches a head however there’s still plenty of time for scary goings-on in the house, and the look and feel of the episode is crafted as well as you could want it by the production team. Director Bill Anderson plays with the conventions of the genre well, and Murray Gold’s soundtrack is unnerving and atmospheric. The set of the house itself (the same house used in Blink, although the show is no stranger to reusing locations) is winningly claustrophobic, allowing the knocks and creaks to never be too far away and used in a way where the danger is ever-present. Where an episode of New Who with similar trappings, Hide, dealt with ghosts, Knock Knock deals with the things that go bump in the night.

Peter Capaldi and Pearl Mackie are on top form, and it’s nice to get fully back in the swing of things after the series’ early stage episodes of character building. The scenes with Bill trying to convince her flat that their lecturer is her grandad are hilarious, with Capaldi at his comedic best, as is his unadulterated glee trying to catch one of the lice. Bill continues to be fantastic, as she learns more about The Doctor (Time Lord information now divulged) and she has plenty of solid development throughout, with her request that The Doctor leave her to experience normality for just a while particularly interesting. She also shows her smarts again, being the one to eventually deduce that the Landlord is the son of Eliza by episode’s end. This is where The Doctor and Bill’s relationship built through the previous, slower episodes pays off- the base level and understanding has been laid-out and now, anything goes! I can’t wait to see how it moves from here (especially as Bill’s student house life lasted a very long time…)

Knock Knock is an assured writing debut on Who for Doctor Foster writer Mike Bartlett, managing to take a tried and tested shell of a concept in the haunted house and layer the Doctor Who skin on superbly well. Oh, and it doesn’t forget to be funny in the middle of all the horror as well, including The Doctor’s lie that he knows Little Mix and Bill’s subsequent embarrassment of having their songs on her Spotify (but leave Little Mix alone, they’re great! *)

Verdict: 8/10

NB: So, whoever is in the vault (and it seems it is a who now…) has a piano, and enjoys stories of young people getting killed. Have we all taken a guess at who it is yet?

*Other opinions are available!