Doctor Who is a genre hopping series. One week it’s a sci-fi epic, the next it’s a western, the next it’s a screwball comedy. But although the show can be many things, it can’t be everything. There are some genres which would stretch the format too far, at least in its TV incarnation. It will never be, for instance, a slasher pic. We’ll never see a Doctor Who martial arts epic.  If there’s a Doctor Who erotic thriller, it will exist only in the dark corners of the internet (and if it already does then please, by all that’s holy, don’t point me towards it).

One genre the show has dabbled with, but which comes close to breaking the show’s format, is post-apocalyptic, where a story is typically set in the aftermath of a global holocaust, society has broken down and a small group of characters struggle for survival. We’re talking Day of the Triffids, Threads, The Road and Mad Max. None of which I’ve seen. Because I dislike the post-apocalyptic genre. I find it makes for unsettling viewing and although I know that’s the point, I don’t enjoy it. So I tend to avoid it.

So it’s a bit annoying when my favourite show occasionally experiments with it. Thankfully, such experiments are rare. There’s a hint of it in Frontios, in which the planet’s inhabitants start looting when the figures of authority start losing control (but thankfully the presence of some big fleshy cockroaches tend to negate any disturbing sense of realism which threatens to emerge).

Old Who’s most concerted effort at it though is Episodes 5 and 6 of Inferno.  They are set in an alternative universe in which an attempt to penetrate the earth’s crust goes disastrously wrong and the Doctor can do nothing – nothing – to save the people around him and strives simply to escape back to his own reality.  Brutally directed by Douglas Camfield and Barry Letts, this story uses compellingly desperate performances and a haunting soundtrack to create a genuinely disturbing vision of humans fighting against the inevitable. The cliffhanger to Episode 6, where the remaining humans watch as a wall of lava creeps irrevocably towards them remains one of Doctor Who’s most visceral moments.

But it doesn’t feel much like Doctor Who, because it’s so grim. And grimness is a characteristic it shares with Turn Left, the Doctor-lite episode from David Tennant’s third season (and interestingly, also set in an alternative reality). Both are as bleak as the series gets, much grimmer than something like say, Earthshock, which features the death of a companion but in other respects is a standard Doctor Who action adventure. So how grim can Doctor Who get?

Turn Left  has two interesting spins on post-apocalyptic fiction. Firstly, the apocalypse in question is caused by the Doctor’s death, itself caused by Donna (Catherine Tate, in a virtuoso performance) taking a seemingly tiny decision to turn right at an intersection instead of left. So Donna, the hero we follow through the story, actually caused all the dreadful events that befall her.

The story’s second twist is that rather than the apocalypse happening at the beginning of the story, here the apocalypse never stops happening. The Doctor is not around to stop a series of alien incursions. As such, disaster is piled upon disaster and millions of people die. It’s unrelenting; while watching this for the first time I wondered mid-episode how far writer Russell T Davies could go. Donna’s own situation deteriorates with each global disaster; she loses her job, then her home and finally all hope.

Donna’s companion through this snowballing series of events is Rose Tyler, played by Billie Piper who returns to the series after a season and a half. Rose has greatly changed since we last saw her.  Here she jumps between dimensions and in and out of the story. She has mysterious foreknowledge of events. She speaks obliquely and won’t reveal her name. She seems untrustworthy. After she encounters Donna for the second time, Donna’s had enough. “I think you should leave me alone”, she warns, coldly.

In script writing terms, Rose turns up regularly in the story’s first two acts, each time revealing more each time and gradually earning Donna’s trust. It’s interesting to see the structure Davies uses here, which is basically:  the Doctor’s death, encounter with Rose, situation worsens, encounter with Rose, situation worsens, encounter with Rose, situation reaches a critical point where Donna makes a decision, encounter with Rose which leads to the story’s climax.

That critical point is interesting. Rose has warned Donna that eventually she will come with her willingly to fix things, but as a result Donna’s going to die. The point where Donna can take no more is when her fellow refugee Rocco and his family are taken away to a labour camp. It’s a heartbreaking scene, in which director Graham Harper chooses shrewdly a shot from the back of the retreating prisoner-laden truck, where we watch Donna chasing helplessly behind it. Finally defeated, she goes with Rose.

It’s a clever choice from Davies, but I can’t help wonder if there’s another catalytic event that would have suited the story even better. Throughout the story, Donna’s been accompanied by her mother Sylvia (Jacqueline King) and her grandfather Wilf (Bernard Cribbins). Cribbins is terrific as a man reliving the terrors of war with both stoicism and mounting dread. But it is King that steals the show, with one of Doctor Who’s best performances.

Sylvia, for all her bluster, has none of her daughter’s or father’s resilience. She slowly shuts down over the course of the episode to the point where she can’t offer her daughter any words of love, only mutely signal her despair. All the signs are pointing to her suicide. Surely that would have led even more fittingly to Donna’s decision to go with Rose and do whatever she needs to make things right.

But the suicide of our hero’s mother is clearly more than Doctor Who’s format can bear. And thus we have the answer to how grim Doctor Who can get; as grim as Turn Left and no more. I, for one, am grateful.

LINKS to Arc of Infinity: I know, I know. Can there be two more different stories than these? But there’s a clear link – both feature the return of a companion. Other than that, of course, they are chalk and cheese!

NEXT TIME: Nobody likes brain alteration! But that’s just what we’ll be served up when we take our first random trip with the sixth Doctor, Mindwarp.

Nothing grim happens in that one, right?