Mike Bartlett pens this episode, Knock Knock, that first debuted on 6 May, 2017. The Doctor (Capaldi) gets pulled into investigating Bill’s (Pearl Mackie) new, rather expansive, and cheap new house, she shares with six others.

The house is overseen by a creepy old Landlord (David Suchet), and the house, while beautiful isn’t without its problems, there are creaky floorboards, a locked off and forbidden tower, and literally creatures crawling out of the wood.

There’s some fun exposition about Time Lords that Bill doesn’t quite believe, and there is a hint of regeneration talk. There is also some fun stuff in the developing friendship between the Doctor and Bill, when she introduces him as her grandfather to her new flatmates.

The episode plays on the usual old dark house stories, it’s spooky, funny, and plays well within the constraints (or lack thereof) of the Who-verse. And like all good Who stories, this one stats as one thing, and becomes another.

Both the Doctor and Bill’s investigation bear fruit, and as the show comes to its climax, the pair figure out what is going on and work to resolve it, even if it comes too late to save Bill’s friends – or does it?

I do like how it starts out as a creepy episode, and then becomes a very sad story as truths are revealed about what is really happening in this house.

And as the episode ends, the Doctor returns to the Vault he is guarding and goes inside, leaving us to wonder who is within. But it really doesn’t take much of a guess to know…

Oxygen was written by Jamie Mathieson and first aired on 13 May, 2017.

Joined by Nardole (Matt Lucas), the Doctor and Bill investigate a strange space station after receiving a distress call, and soon find something sinister about the spacecuits they are wearing as well as the ones moving around the station.

It seems air needs to be paid for in the suits, and even should you run out of air, and die, the suits keep operating. The station is literally filled with the walking dead.

The episode’s visuals, especially the opening sequence are really solid – how far we’ve come from the shakey models of the past.

We also learned that the Doctor swore an oath to himself to protect the Vault and Nardole is there to enforce it. But, of course, the lure of the universe draws him into adventure again and again.

There are some interesting questions posed by this episode, despite its fun trappings; there is the cost of goods, the charging of natural resources (when they aren’t natural in space), profit margins, capitalism, and common decency.

It also introduces a character arc for the Doctor when he becomes blind, an affliction that will be around for an episode or two.

Next week introduces a new baddie in one of my favourite episodes of the tenth series, Extremis.