It feels like a while since we had a good old fashioned spooky episode of Doctor Who, does’t it? The last one was probably Heaven Sent, but that had a lot more going for it than the creepy factor. Knock-Knock is a different kettle of fish that brings classic horror vibes into modern Doctor Who, bristling with emotion.

Peter Capaldi and Pearl Mackie’s performances have been widely praised, and this episode continued to showcase their talents. However, the writing left it feeling slightly hollow and I came away with the feeling this hadn’t been written for Bill.


This episode falls into a common Moffatism; suddenly introducing new characters and expecting us to care about them for no reason. Bill’s apparent best friend turns up having never been mentioned or seen before. Moreover, Bill is moving out, a big deal for a young person, yet we don’t see any interaction with her family over it.

After the first episode did so much to establish Bill’s life setting, it seems jarring to suddenly ignore what has already been established. We got to see Bill’s foster-mother, and got a sense of her homelife, but it felt very much like something that ought to be built on. Here was a perfect opportunity, but it was wasted.

If we had seen more of Bill’s friends before, built them up and given us a reason to care about them, this episode’s impact would have been much more powerful. As it was, Shireen (Mandeep Dhillon) ended up being a somewhat blank canvas. Which is a tremendous shame as Mandeep Dhillon is a great actress and deserved better; here’s hoping we see more of her.

What’s more, the resolution, once again, felt a little flat. Suddenly all these people we didn’t really have time to care about before the died are brought back. Hurray? I guess?

The housemates seem less like characters we’re supposed to care about and more like cannon fodder for the monster. Moffat is a great fan of the ‘everybody lives’ ending, but it loses its power when you’ve already treated ‘everybody’ like disposable plot threads.

Whats more, Bill doesn’t seem herself in this episode. The curious, question asking, bright eyed girl we saw taking on the robots and puddle monsters seems like a completely different character. Why the sudden hostility towards the Doctor? If Bill was worried about the dangers the Doctor brings, and how that might affect her friends, it would have been nice to see that.


Creatures living in the walls is nothing new in Doctor Who. But this was done well and gives the episode a tremendous atmosphere. The sounds, suspense, and shadows were all used well. However, there was a real trick missed that again left me feeling that this episode’s full potential hadn’t been exploited.

The wooden body of Eliza is some seriously good prosthetic work (if it isn’t CGI), and the fact that it wasn’t utilised more is kind of disappointing. With its frazzled hair and unsettling appearance, this could have haunted children’s nightmares if only it had appeared elsewhere. Perhaps if she had moved about the house, scouting for the Dryad bugs, appearing suddenly out of walls, or at the end of dark corridors.

Speaking of the Dryads – which looked a bit like Cybermats – they were an interesting choice. Obviously intended to look like woodlice, so the next time a young Doctor Who fan sees one, they might have a little scare.

When the walls and doors are monsters, nowhere is safe. Again, that’s a concept they could have done more with; have the characters slowly discover there’s nowhere to hide. Every bit of wood is suddenly a danger, every door, every wall, and even the floor could get you!


I will admit that the resolution was kind of clever. Not perfect, but a nice twist, even though it leaves a lot of questions. So he was her son, not her father all along? How did she not notice this? Wasn’t he a young boy for most of their time together? Didn’t she see him grow up? If the Dryads are affecting her memory, that needed to be more explicit.

There was real emotional resonance in their final scenes, though. Mariah Gale and David Suchet are fine actors at the tops of their game, so they brought a lot of weight to it. Having the Doctor stand by and watch two people disintegrate without showing sadness was also somewhat harrowing. Perhaps this is a callback to his darker side coming through.

Incidentally, when Bill saw her friend Shireen disintegrate, I had expected much more of a reaction from her. Last week, she was hit hard by the death of a stranger. Here this is supposed to be a close friend of her’s, yet she hardly reacts. This is not the fault of Pearl Mackie, but of the writers and director, I think. We know Pearl can do this, so to fail to have her react the way she ought to was jarring.

The Ongoing Mystery

I was just starting to be irked by this whole Vault mystery, but this episode saved it a little. My frustration was that there were absolutely no clues, so there was no point even trying to guess at its resolution. But here we finally got some breadcrumbs.

We now know the vault contains a person – or some sort of intelligence. It likes music, and Chinese Food. We know it is a person – or thing – with which the Doctor can communicate affably. The use of ‘pop goes the weasel’ might suggest something of who this person or entity is.

Let us hope that this will only build yet further and reel the audience in.


Sophie Aldred on Pearl Mackie 

Smile – Doctor Who Review

The Pilot – Doctor Who Review