Over the years, Doctor Who has excelled at turning the ordinary into the extraordinarily creepy: statues, shadows, cracks... Doctor Who Season 10 Episode 5 added creaky floorboards to the ever-growing list.

Throw in an old house, alien beetles, and a very sad story and you have a recipe for even more nightmare fodder.

David Suchet, probably most well know for playing Agatha Christie's fictional Belgian detective Hercule Poirot between 1989 and 2013, gave an excellent turn as The Caretaker.

Part of the deep tragedy of the story came in that despite the decades that passed, Suchet's character never managed to grow beyond his emotional dependence on his mother Eliza.

Even in the end, when she urged him to leave, to find a life for himself, he refused. He didn't know how to exist without her, to the point where his character didn't even have a proper name at all.

Hope is its own form of cruelty.

The Caretaker

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He never grew up; he was still that sad, lonely little boy who didn't want to lose his mother. Unfortunately, such things are an inevitable part of life. None of us lives forever.

The Caretaker's inability to accept his mother's mortality in turn resulted in the tragic ends of all those other would-be lodgers, too.

I confess, I'm not normally one for scary movies or the like, so this episode was a bit outside my usual fare. To be fair, though, it wasn't exactly much worse than gas-mask zombies or flesh-eating shadows.

On the other hand, the staircase in my house had a creak to it...

Gee, thanks a lot, Mike Bartlett and Steven Moffat.

If I have one major complaint about the episode itself, it rests in the audio mixing -- I found it awfully hard to make out some of the dialogue at times.

If I had a minor complaint, it would be that this is about the third episode in a row with barely any Nardole in it! Matt Lucas is stellar, and I hope that his character finds more action next time 'round.

Honestly, I loved his quip when the Doctor returned to the Vault:

You don’t have to go to outer space to find monsters. There’s plenty of things that wanna kill you right here on Earth!

Nardole

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Rather ominous, if true!

Speaking of the Vault, we got confirmation that there is indeed someone locked up in there. Someone who plays piano, apparently. And the Doctor appeared to be on at least non-violent terms with said Someone. 

Cue rampant speculation! (Currently, most bets are on either the Master/Missy or the Doctor's granddaughter Susan.)

I would imagine that there is some disagreement over whether or not Bill making use of the TARDIS's mundane utility as a moving van is a good thing or not.

From an in-universe perspective, given our beloved time machine's track record... if it dropped me off where I wanted to be, I'd definitely reconsider wanting to be there, because something dreadful is about to happen.

From a viewer's perspective... well, I thought it was pretty funny, if somewhat ill-advised.

On a side note, did anyone hear if the Doctor remarked about his sonic screwdriver still being ineffective against wood? (Because it would explain a thing or two here.)

The screwdriver actually saw very little use in this episode; Whovians who consider the Doctor's favorite tool to be a storytelling crutch were likely happy over this!

Early on, we got specific references to both the Time Lords and regeneration; we also see that the Doctor's exceptionally hungry at the end, and hunger is often associated with regeneration.

Could these be clues and hints leading up to a regeneration at the end of the season? Time will tell.

Be sure to stop by our Doctor Who quotes page for some of the notable lines from this episode!

Oh, in case you were curious, dryads come from Greek mythology: they are supernatural spirits associated with trees, especially oak trees, and tend to be very shy around humans.

Don't forget to watch Doctor Who online if you missed it! And be sure to tune in Saturday, May 13, 2017 at 9/8c on BBC America for Doctor Who Season 10 Episode 5, "Oxygen"!

What did you think of "Knock Knock"? Was it sufficiently creepy, or was it a yawn? Did you find the antagonist worthy of pity or scorn? Let us know in the comments section below!