Doctor Who: Thin Ice (S10E03) pits race against time travel.

Bill’s real world nous and sci-fi savvy is proving to be a real asset to the current season of Doctor Who. After last week’s detour into whimsical fairy tale storytelling, “Thin ice” brings us solidly back to a more grounded Who, and adds a dash of realism that has often been lacking in the series’ fifty-four year history.

Having landed in 1814 London during the last frost fair, the Doctor and Bill quickly discover that everything is not as it seems. Something is lurking beneath the ice and as people continue to disappear mysteriously, the Doctor begins to suspect that the real monster isn’t under the frozen Thames at all…

Returning writer Sarah Dollard (“Face The Raven”) once again brings bags of atmosphere and ideas into play in this curious hybrid which almost qualifies as that rarest of Whovian delights, the pure historical. Any period longings for the Paternoster Gang are quickly snuffed out thanks to the serious tone of the adventure and, especially, the conversations between Bill and the Doctor. Bill’s willingness to confront the Doctor with the difficult questions not only about time travel mechanics (hello, butterfly effect) but the sociological implications of the historical past and how it could prove problematic at best provides the series with a powerful new way to continue Moffat’s ongoing efforts to deconstruct the series’ mythology, all the while carefully rebuilding and strengthening it as he does so.

The Doctor’s blunt and pithy denunciation of humanity’s whitewashed history is quite a momentous moment, casually but indelibly delivered. It was an issue which was largely ducked during Martha’s time with The Doctor so it’s gratifying to have it explicitly acknowledged even if it may potentially complicate adventures in Earth’s past for a future non-white Doctor. There’s no denying that the real villain of “Thin Ice”, once they are revealed, is all the more monstrous because of their vicious prejudice.

Although there are significant echoes of Season Five’s “The Beast Below”, this is a very different creation, with a very different outcome. The Twelfth Doctor and Bill are shaping up to be one of the very best TARDIS crews in the series’ history, especially when they’ve got material as good as this to work with. The tagged on scenes at the end with Nardole were an unwelcome intrusion even though they at least hinted at developments behind the vault door. Next week’s preview, however, looks like it’s going to reset the limits of what “Doctor Who” can get away with in an early evening family TV slot once again.