★★★★ The Doctor had a telling line at the start of this series: “Hardly anything’s evil. Most things are hungry. Hungry can look a lot like evil from the wrong end of the cutlery.” Hunger or consumption, in particular the ingestion of humans, has become a theme of series ten. In episode one, Heather was consumed by an oily puddle looking for a pilot. In Smile, colonists were atomised by microbots and turned into fertiliser. In Thin Ice, Londoners were gobbled up by a giant serpent and turned into fuel-poo. And now, in Knock Knock, alien lice devour students to nourish some woodwork and the wooden woman, Eliza. None of these actions was “evil”. But a lot of the devouring on display here is enough to put you off your own supper.


I’ve always relished Old Dark House spine-tinglers and ghost stories, from, well, The Old Dark House (the warped James Whale classic of 1932) to The Cat and the Canary (especially the Bob Hope version), and even The Laurel-Hardy Murder Case – movies that managed to be funny as well as macabre, with people goofing about in the dark and tumbling through wooden panels. In his Doctor Who debut, Mike Bartlett has people becoming wooden panels – and being shredded by alien lice.

There are flesh-crawling moments aplenty but, despite any jokiness implied by the title, Knock Knock is only fleetingly funny. For my tastes, it could have mined much more black humour. As it is, there’s the amusement of seeing your own youth flashed back at you. How many of us, especially as students, have been shown round diabolical rental properties, made do with the shortcomings of a low-rent last resort and been unnerved by a creepy landlord?

David Suchet could have gone larger, camper with this, but doesn’t overplay it. He makes the Landlord – we never learn his name – plausible, almost kindly, just on the verge of sinister. He gives great tuning fork. Although responsible for the demise of many tenants, by the end he’s allowed to become a tragic figure. Doctor Who doesn’t go in for big-name guest actors often these days, so it’s good to have a turn from Suchet, our generation’s No 1 Poirot of course and, for me, the finest Salieri in Amadeus. What a voice.

It’s also amusing how Bill doesn’t mind the Doctor moving all her gear in the Tardis but really doesn’t want him cramping her style in her new pad. We’ve all been there at some stage with older well-meaning relatives – and to his dismay for the first time in centuries the Doctor becomes someone’s grandfather. Bill’s buddies think he’s cool (“Oh, wow, Doctor. Legend!”), but she explains, as kindly as she can, “This is the bit of my life you’re not in.” He doesn’t take the hint, immediately sensing that this house is a concern.

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The students’ woes aren’t limited to freaky draughts, the 1930s kitchen and power sockets, a lack of central heating or mobile signal; it’s the fabric of the building that’s the trouble, from creaking floorboards to woodwork alive with voracious bugs – a “total infestation” of what the Doctor dubs “Dryads. I can’t just call them lice.” If you were already an insectophobe, you’re probably now developing xylophobia – an irrational fear of wood.

Doctor Who has presented wooden creatures before. Two Matt Smith episodes spring to mind: The Doctor, the Widow and the Wardrobe in 2011 and Hide in 2013. Eliza, the oaken lady in the attic tower, is a splendid creation. Her slow emergence from behind a shutter would have spooked me as a kid. The prosthetics and costume design manage to make Eliza look both horrible and beautiful. And Mariah Gale’s voice has an ethereal timbre that softens any menace.

I wonder if Mike Bartlett was inspired by David Lynch’s early short film, The Grandmother, the tale of an abused boy who grows a tree-like relative in the attic of a bleak house. Watch it if you dare. It’s 20 times more disturbing than anything you’ll find in Doctor Who.

For the first 35 minutes or so of Knock Knock I’m enthralled. Unfortunately, it show signs of collapsing like a soufflé during the denouement. I don’t swallow the abrupt switch from a father/daughter relationship to one of son/mother between the Landlord and Eliza. She may be half-blind, being a tree lady, but how and when did she start believing “my little boy” was “my father”. Why did he pretend? What happened to the father?

Are six humans every 20 years really sufficient to nourish the house, the bugs and Eliza? We’re asked to accept a lot of nonsense, especially the lice “interacting at a cellular level”, but it’s a stretch to think that as Eliza sacrifices herself she can persuade them to reassemble all of Bill’s chums – their bodies, hair, shoes and clothing – so that everyone escapes the house unscathed. I’d have been far happier with an unhappy ending. And yet I’m dismayed that, as the house crumbles, Bill loses all her knick-knacks, including the treasured photos of her mum that the Doctor sourced for her only weeks ago.

Right after its BBC1 debut, UK viewers have the chance to listen to this episode as a binaural edition (some kind of enhanced surround-sound) on BBC iPlayer – apparently best appreciated through a computer and with headphones. This may read like a cunning ploy to ratchet up the ratings, but Knock Knock does have a rich soundscape. There’s all that creaking, scuttling and bumping in the night. Suchet bonging his tuning fork.

The music is diverse too. Bill seems to live her life to Little Mix (The X Factor-winning girl band). Composer Murray Gold, who’s veered away from orchestral bombast lately, has produced a moody score. And, finally, in the Doctor’s vault we hear a mystery pianist – actually Murray Gold again – playing Beethoven’s Für Elise. See what they did there?


If you’re curious about the Landlord’s house, and its real location, executive producer Brian Minchin tells me: “The exterior is a house in Newport, while the interiors are a mixture of two houses and sets.” I clocked that it looked like the looming property on Fields Park Avenue used in the classic 2007 episode Blink. Well, almost. Brian clarifies: “It’s not the same one! It’s connected to the Blink house, but it’s a different owner and different house. The cellar [in Knock Knock] is, however, the cellar of the Blink house. But confusingly not the cellar used in Blink, which was a set.”


Every story since 1963 reviewed in RT's Doctor Who Story Guide