"The Crimson Horror" is a fantastic example of just how much fun Doctor Who can be when it really keeps its story focussed and aims to deliver as an exciting adventure that's full of intrigue and laughs. This is easily the strongest script from Mark Gatiss so far (particularly impressive as it comes so soon after "Cold War," which is another great episode) and it moves with a wonderful pace while being funnier and more involving than I've found this series to be capable of in recent weeks.
You may (or, more likely, may not) remember that I greatly enjoyed the most recent Christmas special, "The Snowmen." What we get here is a similar kind of instalment, not just because of its Victorian setting and that it brings back the brilliant trio of Madame Vastra, Jenny and Strax but because its mystery seems to unravel in a similar fashion and its able to craft a memorable villainous presence in a short space of time. Much of that is down to an excellent performance from guest star Diana Rigg, who plays the evil Mrs Gillyflower. Rigg's daughter Rachael Stirling also features as Gillyflower's daughter, Ada, a character with an arc that ends up being more emotionally resonant than I expected it to be.
Perhaps one of the most impressive things about "The Crimson Horror" is that the Doctor himself hardly has a part to play for a decent chunk of the story and this one is as much (if not more) about the supporting figures as it is about him. We begin the episode following Vastra, Jenny and Strax and get to see how they work to solve mysteries without the Doctor's aid. Their methods are much less frantic and play out more like espionage but are no less entertaining. When the Doctor does start to have a part to play, he's put in challenging positions that force him to think on his feet and this provides some of the most lively material that Matt Smith has had to work with in some time.
So, the Doctor then very rapidly recounts any and all necessary backstory to Jenny (this comes with a enjoyable stylistic twist too). It seems Gillyflower is sending people to unexplained deaths that leave their skin completely red, a condition that has become known as the "crimson horror." Both the Doctor and Clara went to investigate but landed themselves separated and in difficult positions. It's interesting to see the Doctor find himself in a spot of trouble that he doesn't have an answer to, and without the help of Jenny he would have certainly been doomed.
As the title indicates, there are horror aspects to this tale too and Gatiss's script succeeds in making every scary moment or shocking revelation hit home. The Doctor's first appearance (and the moment where his hand reaches through the door to Ada) is at once surprising and grim, as is the reveal later in the episode of the true nature of the villain. There's some rather creepy and disgusting stuff here, but it's well-balanced with the humour and it fits wonderfully into the aesthetic design of this story and its setting in Victorian Yorkshire.
The gags and funny lines in "The Crimson Horror" might be some of my favourites yet and some are very memorable. I can imagine some found it a little cheesy, but that small joke with the kid giving directions being called Thomas Thomas makes me laugh far more than it has any right to. The general atmosphere of this episode is definitely tonally suited to frequent instances of amusement: Strax is on terrific form, there are some brilliant recurring jokes and the actors settle into a great rhythm that brings out some great lighthearted interplay between the characters.
With that surprising final scene, a confrontation that I've been hoping for between the Doctor and Clara seems likely to come about sooner rather than later. I'm uncomfortable with the level of deception that he has maintained and I'd like to see it come to an end soon. It is interesting to see Jenny's reaction to the appearance of Clara and the Doctor's own answer to Jenny's questioning suggests that he's maybe beginning to worry less about Clara as a mystery because he now cares for her as a person.
Ultimately, this is a really strong episode that works because it is simple in its execution and gives itself room to breathe and just have fun. It's exciting, action-packed and frequently hilarious. At this point, Vastra, Jenny and Strax are so enjoyable that they've done enough to justify why so many see the potential for a spinoff focussed on them. I like that the episode keeps itself from being too serious but also manages to feel like a real adventure by its end. It does a great job of advancing the overarching storyline too, keeping things exciting as we move towards the end of the series. I'm sure some may have found this a little too throwaway and inconsequential but this is exactly the type of episode I watch Doctor Who for and I'm really taken by its charming playfulness.