Not quite sure what to make of this one.
It’s a mostly well-executed tale of a road not taken, peppered with allusions to just about every major event in modern Who history and spiced up by the SF device of Rose’s interventions and the Evil Space Beetle. For an RTD script it’s surprisingly low key, the music isn’t terrible, and generally speaking Catherine Tate does a reasonable job of suggesting an earlier, spikier Donna without losing the core of the current iteration of the character.
The sheer darkness of the alternate history of the Earth is remarkable, recalling last season’s devastated Earth under the Master’s dominion but in a far more gradual and realistic way. I don’t quite believe the idea of concentration camps for immigrants but it’s a strong image that wasn’t hammered home TOO unsubtly.
It’s almost entirely dispensable, almost entirely prelude, and serves only to convey a small nugget of data to the Doctor which, had Donna never encountered the Evil Space Beetle, would not have been possible. Dramatically the parallel history may be well-executed but it comes too quickly on the heels of Donna’s alternate life in ‘Forest of the Dead’.
IIRC I thought the Titanic crashing would wipe out all life on Earth? Maybe Torchwood fixed that too. I’m sure this wasn’t the only potential plot hole in the alternate worldbuilding.
More importantly, if Rose could simply splice the Bad Wolf words into history in that way, why was any of this necessary and why has she been shouting impotently on various TV screens all season? And when exactly did she do the splicing? Back when she was linked into the space-time vortex in Parting of the Ways? Mighty convenient. Also, why did it suddenly appear now instead of having always been there? There’s no logic to this at all that I can see, just a cool idea and plenty of Russell T Davies’ patent bluster. Also Murray Gold cranks the music up to “SEASON FINALE” mode at the end.
Edit: Also, if all it took to put history to rights was a road accident, why did it even have to be Donna who went back?
THE OTHER STUFF
Despite the ending descending into Total Bollocks Overdrive (mainly through Rose helpfully having a Total Bollocks Overdrive machine and switching it on), it’s a mostly well-realised and effective episode.
It’s obviously the Doctor-lite episode of the season, but splitting this and last week’s Donna-lite episode is a smart move that disguises what they’re doing far more than in past seasons. It successfully reintroduces an older, more self-assured Rose and impresses upon us the seriousness of the threat about to descend. And of course we’re now more clear than ever that Donna is IMPORTANT and also DOOMED. It also pays off the “there’s something on your back” foreshadowing from the Pompeiian psychic.
And last but not least: Cloister Bell!
As for next week, we’re gleefully shown every recurring or spin-off character ever to appear on the show. This can only get messy.