Doctor Who sets up the end of season 10 with an outer space adventure that reintroduces one of the Doctor's classic foes.

For much of season 10, Doctor Who has been setting up the end run of Peter Capaldi and showrunner Steven Moffat. Much of that has centered on the mysterious vault housing Missy, a reveal that was, let's say, perhaps not stunning as the season's early episodes teased. Still, Missy's importance to the season's end was a foregone conclusion once her presence was confirmed. Missy, and the promise of John Simm making his return to the series as the Master, adds a kind of excitement to the final two episodes of the season, one that, knowing what we know about both characters and that the series is headed for a major creative overhaul with season 11, helps to assuage any concern that knowledge of Simm's return might spoil the adventure that lies ahead.

That certainly is the case, as the penultimate season 10 episode 'World Enough & Time' offers a compelling set of circumstances in which the Doctor, Bill, Nardole, and even Missy are confronted by a group of Cybermen while also dealing with a massive spaceship caught in the gravity well of a black hole. It's a terrific set up for an episode of Doctor Who, as the various moving parts require a multitude of decisions to be made by the characters in question, and, in this rare instance, it causes a rash one to be made by the Doctor himself.

The biggest surprise is, of course, the one that everyone saw coming, largely because the return of John Simm was a big part of selling the episode. Like the Master's return to Doctor Who, Simm, as well as Moffat and Rachel Talalay – who wrote and directed the episode, respectively – tease out the characters… unmasking. Buried beneath layers of latex, some fake hair, and a heavy accent. The Master is first introduced as Mr. Razor, a sort of custodian on the massive spaceship. It's a long – very long – con he's playing when he rescues Bill after an alien with an itchy trigger finger shoots her.

The attempt to kill Bill is an appropriate set of stakes for the penultimate episode of the season (and, yes, there is the Christmas Special, but still). Moffat is up to his usual tricks, weaving in several different timelines in order to set the stage for Bill to fall into the Master's hands and trigger his very patient plan. The inclusion of a the scene where Bill and the Doctor just talk, while eating on a park bench, is a nice way to introduce Bill's fears about their travels and to underline the huge responsibility that having a companion is to the Doctor. The discussion might be a little too on point, with regard to the fate that awaits Bill on board the ship, as the Doctor takes pains to reiterate the frailty of the human body – especially its lack of a backup heart – but what are you going to do in an episode that involves "the genesis of the Cybermen"?

More so than most episodes this season, 'World Enough & Time' has incredible fun with its concept and manages to offer a satisfying emotional payoff. Granted, it ends on a cliffhanger – several, really, considering Bill's predicament, and the opening scene is the Doctor trying to stave off regeneration – but the hour doesn't read like it's pure set up for the finale everyone knew was coming. Doctor Who is such a enduring series that it can be forgiven for playing to the audience's expectations to a certain degree. It's when the hour finds a way to tell a very Doctor Who-like story – one underlined by the behind-the-scenes changes on the horizon – and weave in an entertaining relationship between Mr. Razor and Bill due entirely to their timey wimey circumstances that makes hours like this worthwhile.

Moffat sets up a scenario where, thanks to its proximity to a black hole, a 400-mile long ship experiences time very differently depending on which of the vessel a character is on. After Bill is snatched from the brink of death by Mr. Razor – and fitted with a telltale mechanical heart to keep kicking – she's essentially imprisoned, watching the Doctor live on an antiquated television monitor as weeks, months, and eventually years go by in the span of a few minutes for the Doctor, Nardole, and Missy. The result is we get to see Bill and Mr. Razor develop a relationship in fast forward. It not only demonstrates just how committed the Master is to the game he's playing, but it plays with Doctor Who's relationship with time in a fascinating kind of way.

All that time lost at the end of the spaceship is nothing to the Doctor, both because he doesn't experience it directly and because, well, being thousands of years old, he experiences time very differently. It's a clever device to get the audience invested in Bill's predicament, and it's one that further underlines the Doctor's failings in protecting Bill. The use of time – or the loss of it – makes 'World Enough and Time' feel like it's of a piece with last season's terrific 'Heaven Sent'. Though it lacks the confessional aspect that made 'Heaven Sent' so effective, the Doctor is again motivated by emotions that don't always bubble to the surface like this.

The double whammy of seeing Bill transformed into a Mondavian Cyberman, and learning it part of the Master's plan sets up a potentially huge finale. Hopefully, there will be a lot more interaction between Michelle Gomez and Simm, as they each have a terrific take on the character and it's a rare treat to see two actors dig into different aspects of the same idea at the same time. Gomez does great work in the early part of the episode, playing to Missy's comedic strengths and teasing fans with knowledge of the Doctor's real name. Her having apparently sided with her past self is a great set up to either an expected heel turn (inasmuch as her current role as semi-reformed evil Time Lord) or a redemption arc that will may wind up being a huge part of Capaldi-Who's legacy on the show.

Next: Doctor Who’s Big Vault Reveal Was a Total Anti-Climax

Doctor Who season 10 concludes next week with 'The Doctor Falls' @9pm on BBC America.

Photos: BBC