One of the many joys of Series 9 of Doctor Who was the way it kept confounding expectations. Just when you thought you knew where the show would take the characters – and you – it thwarted you, and them. (One of my favorite examples was “Before the Flood.” When a Part 1 ends with your main character turned into a ghost, the last thing you expect to see at the beginning of Part 2 is that same main character playing an electric guitar and going on about Beethoven. But it was PERFECT.)

By now, we all know this season ended with Twelve losing Clara, getting her back, and finally letting her go. Together, those three episodes put him, her, and us through an emotional wringer. So it would make sense that the Christmas special would lighten up and allow all of us to enjoy a holiday romp.

And it would also make sense that Steven Moffat would confound us once again. Love or hate him, it’s why we keep watching him.

Instead, he gave us exactly what we wanted. And needed.

I won’t spend too much time on the plot of “The Husbands of River Song.” It’s another silly McGuffin that exists solely to get us to the point of the episode: the reunion of the Doctor with his on-again/off-again/just-what-the-heck-are-they-again love interest, the aforementioned Professor Song.

This time, she’s married to a despotic cyborg, while scheming to get her hands on a diamond that’s currently buried in a very unfortunate spot for said cyborg. And when her assistant (a very funny Matt Lucas) brings her a “surgeon” to help her in her plan, she has absolutely no idea that he’s not that kind of doctor…

And that’s really all you need to know about the story. This episode (directed with great energy and flair by Douglas Mackinnon, whose past credits include Series 8’s standard-bearer, “Flatline”) isn’t really about any of that. It’s about getting River and Twelve together to banter and try to make sense of their relationship. And more than that, it’s about letting Alex Kingston and Peter Capaldi have fun.

I’ve had mixed responses to River over the years. When she first arrived to befuddle Ten in “Silence in the Library,” she was wonderful, and her fate in “Forest of the Dead” brought welcome depth and poignancy to the series. Through her, we came to understand the weight The Doctor bears, the toll every ending takes on him.

When she returned to tango with Eleven, so much of that poignancy was gone, and River (like Clara at first) was more a plot device than a character. (This reached a low point in Series 6 – the less said about “Let’s Kill Hitler,” the better). But her last appearance, in Series 7’s “The Name of the Doctor,” began to restore some of the dimension and pathos to River and her relationship with The Doctor.

“The Husbands of River Song” restores the rest of it. There’s more energy and enthusiasm in Kingston’s performance than I’ve seen in a long time. Much of it, of course, comes from getting to spar with Capaldi (you’d be hard pressed to find a more generous actor to work next to), but much of it is also in the script. After so many heavy-handed episodes, Moffat writes River with a much lighter hand for the special. When she thinks she’s just dealing with some clueless surgeon – really, whenever she thinks she has the upper hand – River is brash and confident and so clearly having fun.

But when she figures out who that surgeon really is, then it gets even better.

(A quick aside: I’ve gone on before about Capaldi’s ability to tear your heart out with a monologue [witness “The Zygon Inversion”]. But in that revelation scene, he needs only two words. If you know anything about River Song, you know EXACTLY what those two words are, and if you know anything about Peter Capaldi, you know he NAILS them.)

The last act of the episode is outstanding, as both River and Twelve realize they’re nearing the end of this adventure… and maybe the end of all their time together. As they try to come to terms with that, we see how much The Doctor has learned from losing Clara. While River rages and pleads for more time, Twelve accepts that the time might just not be there. And he makes amends with a beautiful final date.

It’s a sweet moment, written and staged and most of all acted with great tenderness. And if this really is the last time we see River, it was a lovely bookend to the first.

For one last time, River Song is poignant again.

And with that, we can call a wrap on Series 9, possibly the most exciting and engaging season I’ve seen since Doctor Who returned. It was a semester’s worth of master classes in plotting, writing, direction, and of course acting. And it leaves me wanting more.

I have no idea what Series 10 will bring. I know only that the moment I think I know will be the moment I’m proven wrong. And that’s an exciting thought.

So I’ll be back next fall to see where Twelve leads us. And I hope you’ll join me.

As always, thank you for following along. Until next time…