This week's Doctor Who was probably the best of the series so far. And it is definitely on the top ten list of Steven Moffat penned episodes. It's a tough one to talk about, given that the things that make it so spectacular are the final reveals. Of course both of these twists have already been partially spoiled by the trailers for the episode, but we can't fault an episode on its marketing. Particularly since the reveals work in spite of partial spoilers. This week sees the return of a couple of old favorites, and boy is it good to see them again.

The episode opens with a tease. The Doctor stepping out of the TARDIS and collapsing in to a patch of snow, he starts to glow as if regenerating. Cut to earlier. The Doctor is giving Missy a chance to be good. He drops her in to a situation that she has to help resolve (with the aid of Nardole and Bill). They land on a gigantic spaceship reversing very slowly away from a blackhole.

Shortly after, cloth-headed figures come up the elevator shafts and kidnap Bill, who gets mortally injured in the fray. Taken below decks to be fixed, Bill befriends a local scamp. Thanks to black-hole time-dilation they spend years working together. In the lower decks a whole city has sprung up, and in the hospitals, technology is being grafted on to people to prepare them for what is being called… the exodus. As the Doctor, Missy and co get closer to the answers, some shocking details are revealed.

"In stories like this Steven Moffat reminds us just why he is showrunner.

Creepy is the watchword with this episode. Everything in it is unsettling as hell. Moffat nails the mysterious slow-burn opening that was a hallmark of the early classic series. Mixed in with that are the visuals, which range from modernized 60s sci-fi to Iron Curtain Russia in aesthetic. The dystopian/utopian contrast is pitched perfectly.

Pacing in this episode is also spot on. Moffat keeps the trickle-drip of information tantalizingly slow, drawing the audience in to the world piece-by-piece. It's likely he knew that the final twists of the episode would get spoiled by marketing, and so he teases them expertly right up until the last possible moment. For all his faults over the years, in stories like this Steven Moffat reminds us just why he is showrunner.

POTENTIAL SPOILER TERRITORY

So, we do need to talk about the twists, but the spoiler warning is up for those who have not seen any trailers for the episode.

The Mondasian Cybermen and John Simm's Master are back this week. And it is wonderful. We don't see them till right at the very end, but the reveal is absolutely (pun intended) masterful. The Cybermen are teased throughout, with cloth head socks, chest units, head bars, and voice modules on display frequently, but never shown altogether. I honestly never thought I'd find these goofy creations scary, but I'm happy to be proven wrong. Moffat, director Rachel Talalay, and their costume/design department have outdone themselves on this one.

Speaking of design, whoever did John Simm's disguise makeup is an evil genius. I was looking for Simm all the way through and honestly didn't spot it until right at the end. Between the prosthetics and the performance, it's impossible to tell who's under there. And doing an old-fashioned "the Master is a Master of disguise" surprise ending is such a brilliantly campy throwback, it becomes a genuine shock. With echoes of Anthony Ainley, and the first Doctor, World Enough and Time hits the cliffhanger bell with both hands and leaves us desperate for next week's fix…