Note: Doctor Who TV’s pre-air views aim to be as detail-free as we reasonably can while still offering a critique, but as everyone’s spoiler sensibilities are different, we advise you read on at your own discretion.

And so begins the opening instalment in what Steven Moffat and co-writers Peter Harness and Toby Whithouse are calling “The Monk Trilogy”. A connected story told over the next three episodes.

The plot kicks into gear with the discovery of the “Veritas”, a book located in the Vatican’s vast hidden library. As the Latin linguists attest, the title promises to reveal the ultimate “truth”, but those who have read it have seemingly died. The Doctor is tasked by the Pope to learn its secrets. However, the Time Lord now lacking his sight – not to mention terrifying monks arriving on the scene – has his work cut out more than ever.

The Moffat-penned introduction to this story is definitely a larger scale offering compared to what we saw from the writer in the Series 10 opener. In fact it feels more like an early era Moffat episode in many ways. It’s not full on “timey-wimey,” but there’s a narrative that jumps back and forth in time, and to an alternate place entirely. It’s a bit more of a head-scratcher than we’ve seen from the writer in a while, leaving you questioning what is really going on throughout.

Of course we should really address the other big promised reveal of the episode: the mystery of what’s inside the vault. Now for fans who have theorised something outlandish, it’s best to keep your expectations in check and think simple to avoid feelings of a let down. There’s still a chance that Moffat is pulling the wool over fans’ eyes and it’s not quite as straightforward as it seems, but presented as is, it’s a bit underwhelming. But at least it’s something occurring now, rather than dragging it out until the finale.

There’s some more fantastic acting from the TARDIS crew this week. Peter Capaldi especially puts in another spectacular performance. Still suffering from blindness, we see the Time Lord in a weaker state than he has been before, but he remains unperturbed to let it slow him down, even as the situations get more and more dangerous. Capaldi completely sells every step of the struggle.

Meanwhile, Bill and Nardole are soon paired up and carry the other section of the plotline as they get pulled into their own investigation and discover some shocking truths. Pearl Mackie and Matt Lucas make for a surprisingly strong duo. We see the “badass” (his words, not ours) side to Nardole as he takes on more of a leadership role. A sentence that seemed very unlikely months ago.

The main foes, the Monks, are a fantastically sinister and intimidating foe, not dissimilar to the Silents. Crucially they’re really the biggest monster of Series 10 that isn’t simply some sort of misunderstood being, or has some other explanation for their evil. For this part at least, they just want to take over Earth and have been planning it for a long, long time.

The other foe is of course Missy, but ‘foe’ is not really the right descriptor. The Time Lady we see here is far removed from her old self. She’s shown in a more sympathetic light than ever before, rather than conducting her latest evil schemes (in fact she’s not connected to the main plotline), at least on the surface. Whether Missy is playing another game remains to be seen. Michelle Gomez is as good as ever, but don’t go expecting too much from the character in this instalment.

Returning director Daniel Nettheim (who last helmed 2015’s Zygon two-parter) gives the episode an expansive scope and look. The library sequences are a visual standout: haunting, with a surreal edge. The Doctor’s literal stumbles in the dark made all the more scarier. The music score this week has a very Bond-ish tone early on, and becomes more ominous as it goes on.

Due to the nature of “Extremis,” essentially being an extended set-up, it would be a little unfair giving a full verdict. There’s a fair amount of questions remaining and a few plot threads left open. But if we conclude anything, it’s that it’s a promising and intriguing start. The real event is still to come…