Hey! You! Yeah, you! I'm talking to you! And so is the Doctor...

The Time Lord doesn't often break the fourth wall: in fact, the only other notable time he did was in The Feast of Steven (1965), at the end of which William Hartnell's First Doctor wished everyone at home a very merry Christmas! To do so is to risk breaking the world's illusion, ie. that the Doctor acknowledges he's a fictional character.

Writer, Toby Whithouse is brave to not only have the Doctor speaking directly to the audience, but to have this as the pre-titles sequence. It'll no doubt split fandom, but very few would argue that the subsequent rock-and-roll version of the theme tune is anything other than fantastic. (After the decidedly dodgy track that's accompanied the titles since Peter Capaldi took over the role, anything would be welcome. We get an instrumental that suits the Twelfth Doctor down to the ground.)

Yep, it's divisive, but it's also exceptional.

It's exciting and captivating, and for anybody who's left with a nasty taste in the mouth, there's an argument to be had that he's not really explaining the bootstrap paradox to us but to Clara Oswald.

This is the perfect introduction to Before the Flood because it gave us a hint about what's to come: timey-wimey elements, explanatory discussions, a slight cheekiness, thought-provoking scenes, and the Doctor on mighty fine form.

Indeed, it's a very exciting and captivating episode as a whole. Sure, it lacks some of the intrigue from last episode and anyone well versed in Doctor Who will already have guessed who is in the stasis chamber and that holograms would be used again. That doesn't entirely matter: there's enough to draw you in and keep you on the edge of your seat.

That's quite an achievement considering the story is packed with exposition-heavy scenes. Someone once said, "show, don't tell", so no doubt Whithouse will get criticism for this. Yet it worked. And what made it work so nicely was the ingenious narrative and engaging character development. (I'm not fond of the "show, don't tell" cliché anyway, but that's beside the point.)

Before the Flood is full of smart ideas, throwing the fairly-standard 'ghost' story in a different direction. That's how you keep a two-parter interesting. Give us something new to look at, some new notions to toy with. This isn't a story about hauntings - it's time travel. It might be set in Scotland, but that doesn't mean we can't have the village, pre-flood, covered in Russian propaganda. And because only a set number of ghosts were in Under the Lake, no one who went back in time could die in Before the Flood, right?

Sadly, we should've known that time is in flux, so of course someone would die in the past, and we're very sad it had to be O'Donnell (Morven Christie), an immediately charismatic, likeable, and intelligent character ideal for travelling in the TARDIS. She had something of Osgood about her, sure, but there was also a hint of Rita, a would-be companion from Whithouse's previous adventure, The God Complex (2011), doomed because the Doctor offered her a place in his space-time ship.

Fortunately, there were proper consequences to her death: added gravitas, sadness, and a further peeling back of the Doctor's motivations.

Arsher Ali showed considerable control as he portrayed Bennett's unspeakable grief and his realisation that the Doctor knew this was going to happen. That was foreshadowed by the electric scene in the TARDIS where the Time Lord asks her to stay there – but knows she won't. He did that to her last episode. He forced all of them to make a choice, to stay and satisfy their own curiosities.

Last series, this alien manner seemed very forced – intended to shock and set Capaldi's Doctor apart from his past regenerations. Yet here it works perfectly. The Doctor has always been like this; the extent to which it shows simply varies depending on incarnation.

It brings to mind further scenes from The God Complex, notably the Eleventh Doctor's seeming manipulation, perhaps unintended, of Amy Pond (Karen Gillan). The two adventures share quite a few qualities, despite appearing largely polarised on the surface. Both are important in the evolution of the Doctor-companion relationships (Clara's angry talk with him on the phone is stunningly acted and scripted); both feature large deceptions where the supposed-enemies seem more like victims; both star Tivolians; and both have memorable scenes of the Doctor hiding from a giant, lumbering beast, which ends in death.

Unlike the Minotaur from The God Complex, however, we don't see enough of the Fisher King, played by the tallest man in Europe, Neil Fingleton, and voiced by comedian-actor, Peter Serafinowicz and Slipknot's Corey Taylor. He's certainly a scary creation, beautifully thought-out and realised. His towering over Capaldi makes him seem a genuine threat, while his malicious streak manifests itself in his using of human souls.

There's something of the deep about him, so here's hoping the dam merely put back his plans, that he will return someday...

The Cold War training outpost is a neat idea as well, but one that's also underused. As a backdrop, it does the job and serves the narrative ably. Director, Daniel O'Hara makes it look interesting and gives us fresh new environs for the story to expand, but it did lack something. Nonetheless, it'll remind long-term fans of 1989's The Curse of Fenric, and that's definitely a positive.

The Faraday Cage concept, too, is used deftly in this episode: a place of safety, certainly until the Doctor realises that Clara's phone won't work in there so she'll have to leave it outside the room and fight through the ghosts if it does ring.

Similarly, Cass (Sophie Stone) is excellent, especially in her determination in making sure Lunn (Zaqi Ismail) is safe. Her picking up the vibrations in the floor when the ghost of Moran (Colin McFarlane) is coming for her is very clever, and again acting, direction, and writing all combine to create a tense, absorbing scene.

The really great thing about Before the Flood is that you thoroughly care about each of these characters. You don't want any of them to die. You feel the weight in Bennett's heart as he stares at O'Donnell's ghost then convinces Lunn to admit his feelings for Cass – because he left it too late for himself.

Toby Whithouse has proven again and again that he's a writer you can rely upon. Not one to go through the motions: he delivers vastly enjoyable scripts that play with expectations and make you truly care about the people involved.

There are definitely things to nit-pick about, but the 40-odd minute duration flies by and this two-parter is simply too enjoyable to rip apart. It remains my favourite Twelfth Doctor serial so far.

Images: BBC.