"Mummy on the Orient Express" is a genuinely horrifying story, set in a charming location. There's the whimsy of an Edwardian train in space, undercut both by the terror of an invisible monster no one seems able to stop and an equally obscured evil mastermind who has brought everyone together.
It's also the first time the Doctor has travelled with Clara since their blazing row in "Kill the Moon," and things get off to a tense start.
Here are a few things to keep an eye out for, the next time you watch:
Jamie Mathieson, who wrote the story, admitted that he hadn't known that the Doctor and Clara would be at loggerheads from the previous episode —"Kill the Moon"— when he delivered his first scripts. He told Den of Geek: "The Clara/Doctor dynamic was always in flux and I think making the end of 'Moon' as severe as it was a fairly late addition, which obviously had a fairly big knock on effect for 'Mummy' and led to the whole 'last hurrah' premise. In my original draft for 'Mummy,' the Doctor and Clara were attempting to have 'time off' from adventuring and trying to ignore the signs that anything was wrong on the train."
"Fairly late in the day Steven [Moffat] added quite a few pieces of character stuff...'I had a wobble' was all Steven. Which is all absolutely as it should be. A showrunner should ensure consistency of character throughout the series."
The Doctor offers Professor Moorhouse a jelly baby in a cigarette case, which is a step up from the usual crumpled paper bag the Fourth Doctor kept his in. A staple of his Fourth incarnation, the jelly babies would pop out of his magically deep pockets as a way of disarming suspicious new people he met. The Second Doctor also had a fondness for them, and was seen eating one in an idle moment in "The Dominators," and even offering one to the Brigadier when he returned to meet his Third incarnation in "The Three Doctors."
This is the first time we've seen actual jelly babies on screen in the new Doctor Who, although the Eleventh Doctor made reference to them in "The Almost People" and the Master did likewise in "The Sound of Drums."
We see that Clara has set her phone to show the image of a stick insect in a top hat when the Doctor calls. Clearly, it's an image she's had on her mind for a while, as she had remonstrated with him in "Listen": "People don't need to be scared by a grey-haired stick insect, but here you are. Sit down, shut up!”
British TV fans will know Frank Skinner, who plays Perkins, very well indeed. As well as being a hugely successful stand-up comedian, he has presented his own chat show, Fantasy Football League — a comedic TV show about soccer — and panel shows such a Room 101. He also happens to be a huge Doctor Who fan, and has already appeared in Peter Davison's 50th anniversary special, The Five(ish) Doctors Reboot.
When the news of his casting was announced, he told the press: "I've got a TARDIS ringtone, a five-foot cardboard Dalek in my bedroom and when I got the call saying they wanted me to read for the part, I was in the back of my tour bus watching episode three of 'The Sensorites.'"
Frank is also one of the few Doctor Who actors to have also enjoyed a No.1 hit single, in the form of "Three Lions," an ode to English football:
There were two scenes cut from the episode due to timing issues. The first was a rant from the Doctor about superstition, following the realization that people had created a little shrine around the scroll, with candles and money and little offerings.
The second showed Maisie on the beach with the Doctor and Clara, and has the Doctor explaining that he took Maisie's pain and suffering away from her when he took on the Mummy.
The Doctor says, "The enemy of my enemy is my friend," as if he's the first person to have come up with the idea, and given his time-travel credentials, he may well be. But the expression is one of the oldest proverbs known to humankind. A version of the sentiment was written in the Arthashastra, a Sanskrit document written about statecraft that was put together (seemingly from multiple authors) in the 4th century BC.
Agatha Christie, whose book Murder on the Orient Express informs some of the basic setup of this story, has informed elements of Doctor Who stories in the past, not the least of which is "The Unicorn and the Wasp" in which she appeared as a character. The Fourth Doctor story "The Robots of Death" was said to have been partly inspired by her story And Then There Were None, while "Terror of the Vervoids" has a plot based on a typical Christie murder mystery and underlines that point by showing one character — Professor Lasky — reading a copy of Murder on the Orient Express.
There are two veterans of classic Doctor Who in this story. Christopher Villers, who plays Professor Moorhouse, previously appeared in the Fifth Doctor's medieval epic "The King's Demons," as Hugh Fitzwilliam, while Janet Henfrey (Mrs. Pitt) was Miss Hardaker in the Seventh Doctor story "The Curse of Fenric."
This isn't the only time the Doctor has ridden the space 'rails'. There's a Doctor Who comic adventure called "Trouble on the Orion Express" which would predate this one, in which the Eleventh Doctor, Amy Pond and Rory Williams took a ride upon the ultra-sleek and modern space train, the Orion Express.
There's a second British comedy legend in this episode. John Sessions, who plays Gus, is primarily known to British viewers as an impressionist and improvisor, and a mainstay of the British version of the improvised comedy show "Whose Line is it Anyway?"
Now go back and read the entire 10 Things You May Not Know About Doctor Who archive.