‘Doctor Who’ recap: ‘Knock Knock’ is a haunted house story with a ‘Psycho’ twist

The Doctor (Peter Capaldi) has already whisked his new companion Bill (Pearl Mackie) forwards and backwards through time, and Bill has been awestruck by their adventures, but this week on “Doctor Who” she just wanted to hang out with her mates in their new house. Of course, in the Whoniverse, even such trivialities as splitting the rent with roommates comes with mortal danger from otherworldly creatures. But as has been the case for every mystery this season so far, the solution turned out to be more complicated than a simple case of good vs. evil.

Written by Mike Bartlett and directed by Bill Anderson, “Knock Knock” premiered on May 6. Read our recap below for the top five takeaways from the new episode.

Renter Beware
The episode opens by introducing us to Bill’s friend Shireen (Mandeep Dhillon), who along with four other pals invites Bill to join their search for a rental house. Without much money at their disposal their options are limited, but as luck would have it they’re met by a nameless Landlord (“Poirot” star David Suchet) who asks, out of the blue, if they would like to rent his spacious estate for a bargain price. They briefly tour his creaky old manse and immediately sign on the dotted line. For just a moment Bill looks at her eager friends with an expression that says, “Is this too good to be true?” but she gives into peer pressure and goes along with them.

Where do I even begin? For starters, a mysterious old man found lurking outside a real estate office who just happens to have a spacious rental for six young tenants raises about a hundred red flags. And a creepy caretaker who invites naive young people to his old house sounds like the start of every horror film ever written. After a few weeks of dangerous adventures with the Doctor, Bill can clearly see the warning signs, but her desire to fit in with friends overrides her spidey sense. It takes less than a day for the house to start trying to eat them, but honestly, given the suspicious way this house fell into their laps, man-eating termites from space wasn’t even the worst possible outcome.

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Bill Needs Space, But the Doctor Wants to Stay
While the Doctor has warned Bill not to “sentimentalize” him, he loves showing the wonders and terrors of the universe to fresh eyes. So he didn’t pick up on the hints — or didn’t want to pick up on them — that Bill wanted time and space apart from him with peers she could better relate to. “I’ll see you later for more exciting TARDIS action,” she tells him, “but basically this is the bit of my life you’re not in.” That’s one thing that the Doctor decidedly lacks: a true peer. So while he’s certainly motivated by the ominous nature of the house, there may be equal parts loneliness in the Doctor’s stubborn insistence on staying with Bill. He wants her to want him there.

The Walls Have Ears … And Eyes, Antennae, and at Least a Dozen Legs
The Doctor first makes the discovery of the alien bugs with one of Bill’s new friends, Harry (Colin Ryan), while agitating the old wood of one of the cupboards. They’re not just living inside the wood and feeding on it like termites. They essentially are the wood, “interacting at a cellular level.” That explains the creaking: the house isn’t just old, it has become a living hive — “an infestation of the dryads,” as the Doctor describes it. But they haven’t been doing it by themselves. The Landlord has kept them fed with a steady diet of delicious tenants, but why?

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A Boy’s Best Friend is His Mother
The Landlord initially explains his motive as an effort to save his dying daughter, Eliza (Mariah Gale). The dryads saved her from an incurable illness and have sustained her ever since, but in order to keep her alive they must be fed. “It’s upsetting, I understand, but father says we have to survive,” says Eliza when we finally meet her. She lives in isolation in the house’s tower, and her body has been petrified into a wooden form from head to toe, which is displayed with Emmy worthy makeup and visual effects that highlight how sad and disturbing her transformation has been.

But there’s one more twist in this horror story that gives it an even more tragic dimension. Eliza has been preserved as a wooden creature for 70 years, but how has her father managed to maintain his human form? The answer to that question isn’t some other kind of magic or technology, but merely the passing of time. In truth, the Landlord is not Eliza’s father — he’s her son. He watched his mother start to slip away, and after discovering the capabilities of the alien creatures he learned how to nurture and control them, and he sacrificed innocent lives just to hold on to his mother — perhaps something Norman Bates (“Psycho”) might have done with a little help from his extraterrestrial friends.

The Landlord seemed at first to be a monster, but we see that even now as an elderly man he’s really just a frightened and desperate little boy. In a heartbreaking scene, Eliza finally comes to understand the truth. She directs the creatures to devour her and her son to restore the lives of Bill’s friends, and the entire house crumbles like “The Fall of the House of Usher” — “There goes the deposit,” says Shireen.

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What’s in the Doctor’s Music Box?
At the end of the episode the Doctor returns to the university and to his mysterious vault. He brusquely dismisses Nardole (Matt Lucas), but not before they hear music coming from inside. “You put a piano in there, why?” asks Nardole. The Doctor refuses to explain before sending Nardole on his way. Then the Doctor says to whoever or whatever is in the vault, “Look, I know you miss it all, but I’m stuck here too, you know. We’re both prisoners. So what do you say? Dinner?” He also promises to tell his interred guest the story of the dryads where “lots of young people get eaten.” The response to that is a gleeful rendition of “Pop Goes the Weasel.”

Whatever is inside the vault has the dexterity to play the piano and the sadism to enjoy the deaths of innocent young people. We already know that John Simm is returning to “Doctor Who” this season as the Master, who is the Doctor’s villainous Time-Lord counterpart. I wouldn’t be the first to speculate that perhaps that’s the answer to this season’s overarching question, “What’s in the box?”

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