The Cybermen Are Coming
Doctor Who (2005): Series 10
The creator of the Twelfth Doctor (played by Peter Capaldi) was meant to act as a kind of reset for the show. A new set of regenerations taking the Doctor back to his old man phased, like how he appeared in the very first serials as the first Doctor (played by William Hartnell), before he would, over time, get progressively younger in appearance once more. Capaldi, then, was expected to play Old Man Doctor in the new series... but it never felt like that quite jelled with where the show was at in Series 8 and Series 9.
I don't blame Clara for this. Her character is fine (even if she does feel like stand-in for Amy Pond), and actress Jenna Coleman is brimming with chemistry. It just didn't feel like she belonged in the era of Twelve. He needed someone different, someone that didn't know him from his previous, "younger" regenerations. He needed someone different to play off of so he could find his own way as the Doctor. Who he really needed, in essence, was Bill Potts (well, okay, and regular assistance from Nardole as well).
Bill (Pearl Mackie), is the Doctor's first true companion that didn't come from any other era. Nardole (Matt Lucas) was really River Song's companion, and then he stuck around. Clara was the Eleventh Doctor's companion. Bill, though, only knew the Doctor. She was a true break from the previous eras, and her adventures with the Doctor, for her short run on the show, gave the series a different vibe, a different feel, the true reset the show was trying for with Twelve that, up to that point, it hadn't yet achieved.
In all the previous incarnations seen in the New Who era, every Doctor was introduced as a "mad man in a box". He didn't have roots, he didn't stay in one location. He was always traveling with his TARDIS. So this setup stated, "this isn't the show you remember. We're doing a new era of Doctor Who." Bill, then, works at the university that the Doctor calls home (and, apparently, has for some 70-plus years). Bill catches the Doctor's attention and, even though the Doctor made a vow to stay on Earth as a guardian, he ends up traveling a bit with Bill, just because.
The reason the Doctor made a vow to stay on Earth was because, as revealed in later episodes of the season, he was guarding the prison of the Master... well, Missy (Michelle Gomez). He had to do it for a thousand years, as the only man that could be trusted to keep her secure. But, in the process, he desperately wanted her to actually change. To evolve. To not just be evil. And over time he started getting through to her. But between his adventures around time and space, and his desire to reform his one-time friend, he might have let his guard down. And when true danger comes, it may spell the end for Twelve.
Series 10 is a breath of fresh air for the series after the much weaker Series 8 and Series 9. Giving the Doctor his own new companions, and setting him in a different location, spin the series in new direction that really works. It's unfortunate that we only get this one series in this style before Twelve regenerates into Thirteen because, frankly, I think this is finally where the Twelfth Doctor finally comes into his own. The character feels more focused, more interested, and not just as a grumpy old Doctor.
What helps is that the series goes in hard on longer-form storytelling. It's not just episodic adventures this time around. The Missy storyline runs through all the episodes, slowly building its mystery until finally she is revealed. And then it keeps going, building up her character, making her interesting, setting its stakes. When, finally, a big, late season twist comes, you actually have to wonder whose side she's really on and just how the story plays out. Missy is the best version of the Master, and they give her the meatiest ideas here to play with.
There are also two multi-episode arcs that play out over the course of the season. The first comes mid way, with the introduction of the Monks. This storyline actually starts a touch earlier, in an episode where the Doctor loses his sight. But it then continues through a three episode tale of an alien race coming to Earth to invade while the Doctor does everything he can to stop them. This arc is solid, and in fact could have been a season finale if, say, we'd gotten two series with Bill and the Doctor instead of just one. It has shades of "Last of the Time Lords" but it's handled much better (for the most part), relying on actual solid character development instead of hopes and prayers and treacle.
But then, a couple of episodes later, the series gets into another multi-episode arc. The Doctor, Bill, Nardole, and the Master end up on a ship trapped at the edge of a black hole. Bill gets injured and taken to a hospital at the other end of the ship, and suddenly we're getting a lesson in time dilatation and physics along with a rollicking adventure. I actually really enjoyed the way this episode played out, with the Doctor giving a two minute speech that, at the other end of the miles-long ship, takes years to play out in slow motion.
And then that late stage twist happens and the whole arc of the series changes. It gets dark, and tragic, and there are plenty of feels to be had all around. This two-parter, "World Enough and Time" and "The Doctor Falls", is a great arc that really makes you care about the Doctor, Bill, and all that they fight for. It's, honestly, one of the best finales for the show during the New Who era and, considering it was also going to mark the departure of showrunner Steven Moffat, it works as an end point for a true era of the show as well.
Of course we would get one more special from Moffat and Capaldi's Twelve before the era truly came to an end, and it built off the end of this series quite nicely. Honestly this was just a great year of solid storytelling, such that even though at the time Capaldi was my least favorite Doctor on the show, this series alone really sold me on him. It did everything it needed to do and, honestly, I wish it had happened earlier in Capaldi's run. His Doctor, with stories like these, could have been one of the greats.