PREVIEW! Doctor Who "The Waters Of Mars"

The TARDIS materialises on the rocky, red surface of Mars - it's a striking off-world vista and an iconic beginning to the Tenth Doctor's next episode. What follows is surprising, distinct and awesome, a story that insists on leading us in unexpected directions right up until the very end, and that in many ways doesn't feel like typical Doctor Who.

We knew there was darkness on the horizon: Russell T Davies and David Tennant told us as much in our recent interview (SFX 189 is on sale now if you want to read it). But as SFX joined them both again this morning at a Soho screening room, we didn't expect something quite so challenging.

Set on Earth's first Mars outpost, Bowie Base One (is that an in-joke?), in November 2059, "The Waters Of Mars" at first seems to have plenty in common with Moon, 2001: A Space Odyssey or Silent Running... it boasts a slightly retro science fiction flavour, all white moulded doors and plenty of talking. In ethos it echoes Who episodes like "The Impossible Planet" or "42". The Doctor stumbles upon the colonists - led by Lindsay Duncan's no-nonsense captain - while exploring Mars (his mission? "Fun!"). But upon learning the date, he remembers his Earth history and realises he's arrived at a critical fixed point in time. Sure enough, an underground Martian glacier releases its ancient Water Zombie infection while the Doctor's trying to extricate himself.

But the drooling maniacs aren't the source of the episode's remarkable emotional impact. We're avoiding spoilers here like bio-domes avoid cracks, but let's just say today's audience was stunned into silence by the moral implications thrown up in the last quarter hour. Character-led developments startled us, leaving us pondering if this sinister, noble, angry chapter will leave younger viewers freaked out.

"Have you ever read or seen Harry Potter?" joked Russell T Davies afterwards, responding to just that question from tabloid journalists in the room. "Children are used to dark stories; Harry goes through worse with his mum and dad! It's a moral tale and a temporal conundrum, but kids will get that. They understand this sort of story entirely."

This was a bold and exciting episode of Doctor Who. It feels light years from "Planet Of The Dead" and it explosively establishes a new mind-set for the Tenth Doctor's last bow this winter. We're already wondering whether Christmas evening might be a little grimmer than usual...

"The Waters Of Mars" is scheduled for broadcast on Sunday 15 November 2009.

Read our interview with Graeme Harper on directing "Waters Of Mars".