Of all the Doctors to star in a Doctor Who version of The Mighty Ducks, Peter Capaldi’s acerbic version seems one of the most unlikely. (Not the most unlikely, which would surely be Hartnell. “What, dear boy? I prefer walking to skating any day.”) Still, that’s what happens in The Girl Who Died, as he becomes responsible for training a group of hopeless Vikings for a fight against a group of relentless alien brutes, the Mire. It’s your classic underdog story, played pretty much for laughs, with Vikings too clumsy, too uncoordinated or too afraid of blood to be of any use.

The laughs can’t last for long though. The stakes are much higher than for a hockey match, football game or Jamaican bobsled team. If the Mire win, everyone in this village dies. The weight of that rests heavily on the Doctor’s shoulders.

This is a great episode for Capaldi, who gets to show that responsibility on every square inch of that deeply lined face. But he also gets to be funny and soulful. My favourite aspect is his ability to hear and translate the cries of a baby. P-Cap sells it. You really believe that he can speak baby, and translate not just the jokey asides about breast milk and nappy changes that Closing Time gave us, but also the primal fears and needs of a newborn. His outlook on the fate of this ragtag bunch is changed irrevocably because of it.

On top of that, he gets to play out the Doctor’s grief and anger when his new friend Ashildr (Maisie Williams) is killed in battle, his furious determination to bring her back to life and the slow, hangover of a realisation that he may have sentenced this young girl to immortality. For a jokey script, it ends on a note of foreboding. In fact, it’s not miles away from the feel of Donald Cotton’s Hartnell stories, with historical settings full of gags which turn serious in the final reel.

But there’s something great about how the Doctor manages to beat the Mire. As Clara (Jenna Coleman) points out to him, teaching people to fight is not his style and she knows he’s not going to win until he comes up with a more Doctorly plan. This he eventually does, and as he says, it’s a doozy, complete with subterfuge, a dance, an elaborate pulley system, space YouTube and a tub of electric eels. Even by the Doctor’s standards, it’s mental. But he proves once again that the bullies and the warmongers can be overcome by using your brain. As essentially Doctor Who as that message is, it can never be said enough.

Then there’s Clara, who’s continuing on her journey to would-be Doctordom. She gets herself transported to the Mire’s spacecraft and straight into a conversation with Odin (David Schofield, who’s fine but oh, it woulda coulda shoulda been BRIAN BLESSED!) in which she very nearly manages to end the story 30 minutes early by scaring him off, with threats of advanced technology and half a pair of sonic sunglasses. And Coleman carries it brilliantly with exactly the sort poise that infuriates fans who hate her getting more screen time than the Doctor.

The other side of Clara shown here is her indispensability in getting the Doctor to win through. She is not so much his teacher, as shown in Into the Dalek, but a sort of motivational coach. When he’s ready to abandon the Vikings because they haven’t had the common sense to take his suggestion about fleeing, she gently questions him until he decides to save them – a decision she knows he’ll make, with some prodding from her. Later, when he’s despairing about the general rubbishness of his fighting force, she presses him to change tactics. She’s a prompt for his actions. Almost his manipulator.

It’s a co-dependent relationship. The Doctor needs Clara in order to function like a hero. Clara needs the Doctor to show her how to become a hero. It’s not exactly a cozy relationship, but between them, they are a functioning team, each making up for the other’s shortcomings. So it makes dramatic sense to throw in a third character to shake them up.

And so to Ashildr, the village’s storyteller and feisty teenage girl. Despite her young age, she’s a catalyst for the story’s big events. It’s her recklessness which leads to the Mire deciding to stay and fight and gives us the Mighty Ducks. It’s her puppetry hobby that inspires the Doctor’s wacky plan with the fake dragon. And it’s her imagination which feeds the illusion of the mighty beast into the Mire’s helmets. In many ways, it’s her story, not just because it’s named after her.

Both the Doctor and Clara are strangely drawn to her. The Doctor, as he explains, is haunted by a kind of future memory of her. Clara seems to have a crush on her (“Fight you for her,” she offers the Doctor at one stage). Both treat her as a potential protégé. In other circumstances, she might have been asked to board the TARDIS as a new companion.

Instead, she becomes the focus of the Doctor’s tempestuous grief, when she dies through a miscalculation in his plan. He breaks his own rules, lets her absorb some Mire technology, resurrects her and makes her immortal. But this tells us nothing new about the Doctor. That he’s a man of great power, that he’ll break his own rules when pushed, that he can take an ordinary person and turn them into a being of universal significance… all this we knew before The Girl Who Died.

But we didn’t know this vengeful god of a Doctor would turn up in the middle of what has been, up to that point, a jaunty historical comedy. After all, this is a story with Odin appearing in the sky straight from Monty Python and comic antics accompanied by the Benny Hill theme. It’s not where you expect to find a portentous immortal being created by an act of Doctorly rage.

That’s OK. This show’s frequently been about contrasting light and dark. And if it’s an uncomfortable mix in this episode, then The Time Meddler, Delta and the Bannermen and The Fires of Pompeii all have something to say about that. The only surprise is that a story-bending character like Ashildr, who will go on to be an ongoing force in the Doctor’s life, and who will eventually split our cozy couple apart, should emerge from such jolly hijinks as this.

Anyway, I best get on with my pitch to Big Finish. It’s called The Mighty Duxatrons. It stars David Bradley as the first Doctor. Emilio Estevez is going to co star. Underdogs as far as the eye can see.

LINK TO The Stolen Earth/Journey’s End: in flashback, we see the tenth Doctor and Donna again.

NEXT TIME: What a stupid fool you are! Let’s play The War Games.