PLEASE NOTE: THIS REVIEW CONTAINS SPOILERS. OUR SPOILER-FREE REVIEW IS HERE.

Let’s do this the wrong way round, because if you’re anything like us, the part of Cold Blood that you’ll be wanting to talk about all happened in the last five or ten minutes.

Up until this point, we’d been treated to an entertaining, involving conclusion to an old-style Doctor Who two-parter. But from the moment the crack appeared again in the wall, and the Doctor actually looked like he was going to bother to explain it, we shot straight back up in our seats.

It’s a good job we did, too. As the Doctor reached into the crack, we couldn’t help thinking we were on the verge of a Utopia moment, where an episode was about to be turned on its head by something happening in its final moments. As it turned out, for once we were absolutely on the money.

Never mind for now what the Doctor pulled out of said crack (we’ll come to that shortly), how about instead the fact that Doctor Who did what it’s been reluctant to do ever since it returned: kill off a major character?

Granted, Rory is hardly assistant rank in the Tardis, but he’s not far off. And when you consider how dramatically Russell T Davies pulled back from even giving one of the assorted characters a scratch in Journey’s End after threatening to bump at least one of them off, then this is radical stuff for Doctor Who.

Because this is, after all, a Saturday teatime show. And yet, for the first time since Adric decided he was going to try and stop a spaceship crashing, a companion character who had travelled with the Doctor for several episodes was killed on his watch. Now granted, it wasn’t the most convincing way to go (there was a bit of a Die Hard ending about Restac crawling through rubble and firing off a shot), but nonetheless, Rory was shot, and Rory went down. Furthermore, the light coming through the crack got him, which most of us, we’d wager, suspect is the way that Rory will come back to life.

Truthfully, we’d be shocked if he didn’t. There’s presumably a reset switch in there somewhere, tied in to the fact that Amy has already forgotten him (and how good a plot device now does having the two of them waving across the valley look?) just as she’s forgotten the likes of the Daleks. But for now, that’s a genuinely shocking conclusion.

And yet, Cold Blood wasn’t finished. Because what’s that the Doctor has in his hand? A piece of the Tardis. That’s going to all come to fruition, no doubt, in the four weeks ahead, yet in truth, we were still in shock at Rory’s death by this point. Nonetheless, Doctor Who still squeezed in another little mystery with the Tardis segment moment before the credits were allowed to roll, and we'll be speculating about what that means for weeks to come.

All on a Saturday teatime.

The episode that had preceded it to this point all of a sudden felt like a different story, albeit still an enjoyable one. It carried on the themes from the previous episode, that of being an old-school-feel Doctor Who adventure. That meant you got corridors to run along (albeit very nicely dressed corridors), moments of perils that are interrupted with seconds to spare, and a race who aren’t as two-dimensional as they first appear.

The Silurians, as we noted last week, haven’t always drawn the longest bit of the straw where Doctor Who is concerned, but they had fine treatment here.

Turns out that they’re as divided and conflicted as the humans they’ve been sharing the planet with, and on each side there’s someone you could call an enemy.

What was surprising was just how far Ambrose was allowed to go in the script, fulfilling the prophecy that one of the humans would kill the Silurian prisoner (making it two genuinely surprising deaths in one episode).

That they did, instantly damaging any hope of brokering the peace deal that Amy, Sildane the Silurian leader and Meera Syal’s Nasreen had sat down to work out (with the Doctor urging them to be the best they could be). There was, to be fair, quite a lot of talking over action in Cold Blood, we should note, but that’s a good thing in this case.

And it led the Doctor to ultimately put the talks on hold, declaring neither side ready for another 1000 years. In short, 1000 years to save the planet. The subtext isn’t too tricky to see here. What was nice, though, was that Nasreen got a really solid end point in the story, and we wonder if she’ll be around when the Silurians are next explored by Doctor Who at some point in the future. It's certainly left something in the tank for the next time we meet them.

With quality mask and creature work that actually allowed the Silurians to emote and the actors underneath to do their stuff, we’re pleased with how well the return of the creatures turned out. These aren’t old style roaring Doctor Who monsters, instead having a backstory that allows them to be woven into more contemporary stories with just a little more depth to them. Writer Chris Chibnall did this well, too.

But still, it’s the ending that’s going to be talked about the most. And perhaps fairly, because until the rug was pulled from under our feet, we were puzzled as to why this was the second two-parter of the series, when the natural home for it appeared to be earlier in the run.

As it turned out, it’s set things up for a fascinating next adventure, the Richard Curtis-scripted Vincent And The Doctor. Taken as a standalone episode, that already had the potential to be intriguing. But given the story threads it now has to weave in – it can’t ignore them, after all – it’s a flat-out must see…

Our review of last week's episode, The Hungry Earth, is here...