Christmas is synonymous with indulging yourself in some unpretentiously glutinous, unadulterated fruit-cake, kicking up your tired heels and letting good sense out the door while saying hello to glittering festivities. The Doctor Who Christmas Special is along the same lines.
After the last few emotionally heavy episodes and (SPOILER) especially after Clara's departure, the series seemed to have made too many demands on your heart strings and tear glands. Not this particular episode though. This is just one unpretentiously light-hearted romp which you could easily rename The Adventures of River Song, given the magnetic presence of Alex Kingston (River Song). For a character whose very timeline is so "timey-wimey' that 'people usually need a flowchart', this episode does a lot in terms of answering FAQs with respect to the only person to truly rival the doctor in terms of intelligence, sass and overall wit. If you're interested you could read or watch more about River's timeline.
The plot is largely predictable, but the jugalbandi between Capaldi's 12 and Kingston's River is inimitable. A surgeon is required for a medical emergency - and who better to attend to this than the Doctor himself? Except it turns out that the patient is King Hydroflax, an intergalactic tyrant of great repute, and his wife is a River Song who has no idea that the Doctor is the Doctor. To add to the mix, the most valuable diamond in the universe (Halassi Androvar) is buried in Hydroflax's head and the Doctor is taxed with its removal. Comedy ensues as River's real plan of removing Hydroflax's head ("I married the diamond") is found out and the bad guys give chase.
Most of the comic sequences leading up to the plot climax deal with a role-reversal of Doctor and companion. After realising that River really cannot recognise him despite the fact that she's instituted a mission called Damsel in Distress (the Doctor being the Damsel in question) to look for him, 12 readily gives in to playing companion to 'Doctor River', who is clearly the driving force in the episode. She even steals the TARDIS as part of her getaway plan in front of a bemused Doctor who realises that this is not the first time she's done so - she even bids him to drink some Aldebaran brandy stashed in a secret corner of the TARDIS main console room. Clearly, there are still some secrets to the TARDIS (psst, like avoiding deck seven) - flying and living in it - that are still a secret to the Doctor himself.
After a pretty neat timey-wimey sequence wherein the duo realise that destroying Hydroflax's head sans his cyborg body will lead to destruction, River flies the TARDIS aboard "The starship Harmony And Redemption, minimum ticket price one billion credits, plus the provable murder of multiple innocent life forms. Suites are reserved for planet-burners." It is here that River plans to auction the diamond to the highest bidder. Things turn ugly when the buyers turn out to be vassals of Hydroflax. The Hydroflax cyborg also emerges with the help of the embodiment of That Slimy Server Who Everyone Hates (Flemming).
The Hydroflax cyborg destroys the originial head because, as a rational android, it realises that with only 7 minutes to live, the king is dead, long live the king. So who's going to sit on the throne? None other than the Doctor of course. But as it were, only his head. It starts to get personal when River is confirmed as a 'known consort' of the Doctor and she finally drops her wise-cracking, swashbuckling exterior for a proud and beautiful rant - River style. She may love the Doctor, but no one said anything about him loving her. Because she argues, his person is as huge and inaccessible as the stars and the moon, loving him means sharing him with the entire universe and that can get very, very lonely. She even asks for a sweep of the entire deck, because she's so sure that he doesn't care about her being in danger.
And that's when it gets fun. Daddy says hi to Mummy with a "Hallo Sweetie" and River finally recognises her Prodigal Doctor. And the plot interrupts with a well-timed meteor shower that destroys most of the main deck - escape plans are cheaper than taxis, after all. It does pay to be an archaeologist from the future. The Hydroflax cyborg too gets his due with the Doctor attaching a miniball with access to the multiverse's finances in their entirety- on his empty head, and he blows up with a plaintive "I don't understand".
The ship nearly crashes but the married couple end up safe and whole (but out cold) in the TARDIS, on the planet Darillium. What's so special about Darillium now? For those who haven't figured it out yet, that is where River and the Doctor have their last night together. Which is also why the Doctor has avoided that night for decades now. The only issue is, the famous restaurant overlooking the singing towers hasn't been built yet-they're at least ten years too early.
No matter - waiting is meaningless when you have a TARDIS and the most valuable diamond in the universe in your pocket. The Doctor smoothly commissions the construction of the restaurant, waits 4 years for the best table and voila- on a certain Christmas-the date occurs.
But River's diary is nearly full and she knows this. And she also knows that the Doctor usually knows how large a diary one would need for their memoirs. We get a sense of their open marriage - bonded across time and space - in the fierce love they share. But like River keeps reiterating, loving the Doctor is like loving a monolith. But while loving a monolith can bring you pain, it also brings its own share of sweet reward. For although this may be the last night River and the Doctor spend together, one night on Darillium is 24 years.
Merry Christmas, everyone.