This week, we’re literally on the edge of destruction, and in the land of fiction. ‘Amy’s Choice’, at first glance, is one of those episodes where the plot is running on the spot. But it’s certainly not running on empty.

Somebody in the production team clearly is taking note of the comparisons between Matt (Smith) and Pat (Troughton): this is an elegantly creepy and sinister episode. It would be good to start a rumour, here, that the original plan was to film it in black and white. Having said that, the plot is all about shades of grey.

Fans who have complained that Rory and Amy show not nearly enough surprise at The Doctor and his world are somewhat missing the point and should be careful what they wish for: it really would be tiresome in this new era of Who for every new character to ask the questions long-term audience members already know the answers to: What’s that? Where are we? When are we? There’s clearly no need for such exposition-heavy dialogue every time someone new turns up in the TARDIS. Toby Whithouse even managed to have a pop at such moaning fans in last week’s ‘The Vampires Of Venice’: ‘I like the bit when somebody says it’s bigger on the inside – I always look forward to that bit’. Also, we should note that such familiarity with The Doctor has already been written into the script: he is, after all, the imaginary friend of their youth.

Another immutable, unchangeable factor in Doctor Who appears to be the fact that we seem not to be able to cope with a companion that’s not a young female. It’s a shoddy rule, and it’s wrong – and it wasn’t always thus. Some of the best companions were male: Ian Chesterson (awkward, correct but courageous) and Jamie McCrimmon (charming, kind, and simply sexy). You get the impression that with imaginative writing, the rules could change, but it certainly seems true that a young man won’t be allowed a long-term residency on the spaceship.

So, this is a rather clever episode. Not in the twisty-turney-timey-wimey elements of the plot – you can’t get through a Steven Moffat-influenced episode of nu-Who without hitting a few clock-melting bits – but in the way that it sets up the possible departure/staying power of Rory. (It’s telling that, despite him being in full companion mode, Arthur Darvill’s name doesn’t make the title credits).

These days, it’s not enough for the boy-companion to simply be a bit wet, and Eccleston’s bullying of Mickey alongside Tennant’s pseudo-jealously of almost anyone else never felt comfortable. So, therefore, we need a bigger and better reason for Amy to choose between her man and her Raggedy Doctor, particularly if, with an advanced pregnancy, she quite literally is bigger on the inside.

We get the fan-boy/DC Comics staple: the all powerful being that presents the main characters with a poisoned chalice, an impossible choice. And none of it is nearly as simple as it seems. Rory here is an excellent companion and the Doctor has genuine affection for him, while there’s (quite deliberately) a few too many scenes when we’re allowed to see the Doctor’s glee at how impossible their situation has become.

A similar episode, in visual style at least, happened way back in the 1960s, when Mr Troughton was on the controls, and the images within the first episode of ‘The Mind Robber’ – an exploding TARDIS, an entirely white, formless dimension, and a cute girl on top of the TARDIS console – have long passed into fan mythos. This episode has at least an equal amount of iconic images, including a stunning ice-drenched TARDIS. It’s all a deliciously scary and at times rather upsetting episode: one of the most adult, really, that the series has ever done, but laced with themes that will have real resonance for the youngsters watching. It’s The Avengers meets ‘Terror Of The Autons’, with enough granny-bashing and joy-riding moments to worry the Daily Mail.

‘Your friends never see you again once they’ve grown up’, The Doctor is told when he looks in the reflection of a rear view mirror to see the villain mocking him. And later, he’s attacked by one companion when a major death occurs and he wasn’t able to help: ‘What is the point of you?’.

If you’re the target audience for the show, this could simply be a scary episode with a good few creepy moments and a plot that wilfully doesn’t make sense for much of its running time. If you’re a jaded, cynical and hardened Doctor Who fan, it might be some of the finest minutes in the TARDIS ever. Those of you who were scared that you were going to get an episode of Timelords Behaving Badly from writer Simon Nye should prepare yourself for a shock. And possibly some tears…

Airs at 6.25pm on Saturday 15th May 2010 on BBC One.