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

The general consensus come the end credits of The Eleventh Hour seemed to be that the new era of Doctor Who was off to a good, solid start (that's a little bit of an understatement). But for me, it’s this second episode I’ve been waiting for, The Beast Below.

For this is the second standalone Steven Moffat-scripted instalment of the series, but the first that’s freed of the need to bring in and introduce two new faces to the show. As such, here we get to find out just what he can do with an early season episode, the kind that’s often forgotten about several weeks down the line.

That won’t be happening here, though. For The Beast Below was very good indeed.

It worked on more than one level too. At heart, it often felt like a traditional old-style Doctor Who episode, with corridors to explore, an enemy observing the Doctor investigating the strangeness around him, and the constant feel of a greater threat waiting to be discovered. Long time followers of the show have seen that kind of build up many times before, and it was fun to see it again here.

But while the structure may have felt familiar, the flesh put on the bones was really something quite special.

Firstly, this was an episode where we saw the imperfections in the relationship between The Doctor and Amy begin to develop. Certainly in the early stages, they appeared to be a solid working match, sharing an upbeat and wide-eyed view of the world.

But in the early stages, Amy starts to probe – most tellingly when asking if the Doctor had ever had children – and she starts to learn about one or two of the gaps in his backstory. We know, of course, about the story of the Time Lords (it was only at Christmas, after all), but to Amy, it’s all fresh.

It also proves to be crucial information in its own way come the denouement of the episode, when – as the Doctor tries to resolve things in the same old way – it takes Amy to work out what’s staring them in the face, because ironically the Doctor can’t.

It was Amy that ultimately adhered more to his rule set, and it was Amy that saved the day. It was really well done, and brought them back together as a working team by the end of the episode. But it’s good to see just a little bit of unease and friction working its way in there. Star-crossed lovers this pair absolutely aren't.

The central story itself was timed to perfection to arrive in the midst of an election campaign in the UK. We find that most of Britain is now a floating spaceship, one without an engine as it transpires, where the people are allowed to know the truth about what’s basically kept them safe, and are given the instant opportunity to either protest or forget once they know the full horror of it. It’s an episode full of choices, and the political subtext is neatly worked in. Society as a whole thus chooses to forget, has their minds wiped, and goes about their everyday lives, freed from knowing what keeps them alive.

It inevitably draws comparison with the Doctor Who team of the late 1980s and the subtexts that they wove into their stories. Moffat has more than picked up the mantle, and crafted it extremely well. Heck, I even got a bit of a vibe of The Happiness Patrol at one point.

But back to The Beast Below. The ongoing message of the series already is to look carefully, and the Doctor’s attention is thus drawn to the Smilers, creatures in boxes that look too clean to be a genuine part of the world. His instinct proves correct, and once more, Steven Moffat comes up with quite an effective, creepy monster. The irony, of course, is it’s not the Smilers that prove to be the main problem.

Instead, it’s those buttons that allow the wiping of knowledge in an instant. They, ultimately, are the biggest enemy in the episode. This is brought terrifically to the fore with the decision that Liz 10 can’t make when she’s put in front of a screen with the option to reign for another decade and keep the status quo, or to free the tortured creature that we learn is powering the starship and abdicate. It takes a youthful mind – Amy’s - to overcome the fear of making that call.

This is an episode that's set to stick in the mind some time after the credits roll, not least the moment where Moffat takes the Doctor into darker territory. For the Doctor’s solution to the dilemma of potentially killing the residents of the British ship or allowing the starwhale creature to remain tortured is to basically mentally kill it. The uneasiness of Matt Smith’s Doctor headed a little into Patrick Troughton territory at this point, and it was great to see.

After all, it arguably took some time to take Tennant’s Doctor this far (culminating, of course, in the wonderful The Waters Of Mars), yet Moffat seems keen to waste little time in exploring the darker sides of the Doctor’s existence. That bodes extremely well, and he also demonstrates why the Doctor has been so missing a full-time assistant over the past year and a half.

On the downside of the episode? Some of the effects work, mainly. It was fine when looking at exteriors of the floating Britain, but it did struggle whenever it had to focus in on the starwhale in any of its forms. If you were being picky, you might also suggest that the character of Liz 10 wasn’t the strongest, but she was well played, and served a crucial story purpose.

Yet, it's hard to really complain, for The Beast Below was a strong and subtlety complex episode. I counted more than one Star Wars nod in there (although that might just be me!), and I loved the way it tied into the next adventure, Victory Of The Daleks (and just how good is that looking?). One adventure flowing wonderfully into the next? More of that please.

Likewise, there's another hint to the series' underlying story arc with the crack we see at the end of the the episode. Is this a hint that we've not seen the last of the Atraxi perhaps? Or are bigger forces at work?

That's for future weeks, though. Most of all here, we loved the way that Steven Moffat took a series of strong ideas, wove them together with a skill that few writers working in television today could manage, and still packed together a 45 minute episode of high quality Saturday night science fiction.

And we couldn’t help thinking that if this is what Steven Moffat can do with episode two of a series run, that we should be in for a hell of a treat by the time his closing two-parter comes around in two months time.

Next time: the Daleks. For once, I can’t wait to see them again…

Our review of last week's episode, The Eleventh Hour, is here.