Inside No 9 review – nothing short of miraculous

The beating heart … Reece Shearsmith and Steve Pemberton in Inside No 9. Photograph: James Stack/BBC/PA

Every episode of Inside No 9 is dramatically different – and every episode is also essentially the same. Reece Shearsmith and Steve Pemberton tend to begin each instalment of their magnificent comedy-horror anthology by summoning a scene of distinctively British mundanity: it’s small, it’s boring, it’s awkward, it’s wryly funny – the workaday greyness sparkles with fragments of laugh-out-loud hilarity. Yet from the start, that tableau of normality bristles with nauseating dread – ultimately, the show will excavate from it a blast or two of terror. We know it’s coming, but we don’t know how and we don’t know when. At this point, Shearsmith and Pemberton have used the formula almost 50 times. That it still produces such grimly fascinating, heart-stoppingly tense and peerlessly clever half-hours of TV is nothing short of miraculous.

Perhaps not wanting to push their luck, Shearsmith and Pemberton are finally nudging the door closed on No 9, as (fittingly) this ninth series airs. It’s a “pause” in production, Pemberton has said, rather than a decisive finale. That noncommittal approach will probably quash hopes for a twist to end all twists: Inside No 9 is notorious for its incredible endings – the sort of shock reveals that make the ground below your feet shift. It would have been fascinating to see how it pulled off its ultimate denouement.

But for now, at least, we have the opening episode of a new series to be getting on with. Once again, a typically humdrum scene is established on a sparsely populated London underground train, but you’d pinch yourself if you really did find yourself sitting in this carriage. It’s like being in a mashup of recent TV hits, with a roll-call of star names to die for: Siobhan Finneran (Happy Valley), Charlie Cooper (This Country), Philippa Dunne (Motherland), Joel Fry (Plebs), Mark Bonnar (Guilt, Catastrophe), Susan Wokoma (Year of the Rabbit) and a practically unrecognisable Matthew Kelly.

Inside No 9 is clearly a dream gig for any actor (later episodes feature Eddie Marsan, Natalie Dormer and Adrian Scarborough). But despite their starry accomplices, Shearsmith and Pemberton remain the beating heart of the show. For all their narrative genius, Inside No 9 would never have worked without the duo’s ability to load their characters with depth and backstory in a matter of seconds. Here, a mustachioed and tweed-jacketed Shearsmith is a man who has retired into a world of meek comfort – his wife (Finneran) squirms against her husband’s late-life conformity – while Pemberton plays a viperish and proudly un-woke drag queen. Before long, Cooper’s homeless man stumbles through the carriage asking for money. The train screeches to a halt. The lights fail. Suddenly, a nurse (Dunne) reports her purse missing. Bonnar – a teacher, seething with barely repressed fury – decides to search everyone to find the culprit. But Fry’s jumpy conspiracy theorist refuses to let him check his bag.

Unlike other episodes, which are often littered with handbrake turns, this time we end up sitting tight for the big reveal. And it’s completely unguessable – that violent shift in perspective executed with aplomb. Unfortunately, though (and it pains me to say this considering how absorbing the rest of the episode is) the actual twist falls a bit flat. While the most successful endings tie together clues secreted throughout, this one seems to come out of nowhere and is far-fetched enough to leave you with more questions than answers. Although this is probably one of Inside No 9’s most meaningful episodes – there’s a thought-provoking political point nestled in there – a reveal is always most skin-crawlingly effective when it feels plausible on a literal level as well as a symbolic one.

However, Shearsmith and Pemberton have five more opportunities to get it bang on, as they have so many times before (future instalments involve an escape room, an Edwardian piano-tuner and strange new neighbours). And an episode of Inside No 9 that leaves you slightly nonplussed is still a hundred times more inventive and affecting than 99% of what is pumped through our screens. Most series drag out their one big twist over 10 hours; this show lavishes us with ingenuity.

Shearsmith and Pemberton have announced a West End show based on the series. Theatre will doubtless add an extra dimension to their hair-raising tales, but it’s TV – with its haunting intimacy – that feels like their natural home. Hopefully, two of the greatest minds to grace our screens won’t be able to stay away for long.

• Inside No 9 aired on BBC Two and is on iPlayer now.