For the first five minutes at least, it looked thoroughly generic. Arthur Flitwick (Steve Pemberton) is back from the shops. He puts a mobile phone on the kitchen table, sticks Symphonic FM on and sets about coddling an egg. The phone rings, there is some sinister but indistinct white noise, the egg explodes in the microwave and the caller rings off. Flitwick redials the last number and what appears to be some vaguely underwhelming domestic farce involving a lost phone and a confused old lady begins to ensue.

It is often said that in the age of Twitter and on-demand streaming, secrets are impossible to keep; shocks are diffuse and signposted; TV is no longer a communal experience. This autumn has presented two strong rebuttals to that idea. First, there was Jed Mercurio’s frantic drama Bodyguard. But on Sunday, the truly audacious live special of Pemberton and Reece Shearsmith’s dark anthology comedy Inside No 9 went further still. You really did have to be there.

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From Flitwick’s phone call onwards, all bets were off. The arrival of Shearsmith’s vicar Reverend Neale saw the manifestation of the first gremlins: the sound disappeared and BBC Two’s continuity announcer intervened. Twitter collectively speculated about P45s on the way to the production crew and the show lost a fifth of its viewers as the less patient gave up the ghost. But the ghost was just getting started. A repeated (largely silent) episode of Inside No 9 began, but soon we were back in real time, in Pemberton and Shearsmith’s dressing room. Shearsmith flicked on the News at 10 where the green and gold flags of Jair Bolsonaro’s celebrating supporters could be glimpsed. Yes, this was actually happening, right now.

This perfectly perplexing half hour of television has been in preparation for a while. The production team have been carefully seeding the show’s central conceit: the haunting of Granada studios. An article appeared in the Sun last week claiming that interventions from deceased Coronation Street stars had been making rehearsals impossible. But even so, what began to unfold was remarkable and unsettling. BBC Two itself appeared to be possessed, stricken by visitations from the studio’s illustrious and traumatic past. From Bobby Davro’s notorious faceplant during the filming of shiny-floor folly Public Enemy Number One to a serious fire during which costumes for The Jewel in The Crown were destroyed, we were suddenly scrolling through an index of Granada-based mishaps. Who knew where it would stop?

Facebook Twitter Pinterest Notorious faceplanter: Bobby Davro Photograph: Cambridge Jones/Getty Images

Were people fooled? However much they might deny it now, yes they were. And actually, what fun to be so playfully toyed with by television; to gaze at your screen and feel genuinely bewildered. But better yet, Shearsmith and Pemberton included us, made us participants. Shearsmith tweeted “Are me and Steve Pemberton on BBC two now?” and people replied. Viewers’ real time reactions became part of the spectacle in a way that felt more profound than usual, possibly because what we had seen had been confounding enough to make speculation unavoidable. Co-star Stephanie Cole’s Wikipedia entry was altered to reflect her sad, on-screen suicide as the possessed studio continued to work its dark magic.

Event TV is a term that is now lazily applied to everything from cookery shows to talent contests. But the Inside No 9 live special really did deserve that description. It is now on BBC iPlayer and is well worth a second (or indeed, first) look. But if you weren’t there at 10pm on Sunday, you missed the essence of it. What the show demonstrated was that in the hands of true masters, modern media networks like Twitter are simply more tools, more colours a writer can add to their palette. The show’s closest relative is probably BBC One’s spectacular 1992 Halloween epic Ghostwatch. But Ghostwatch was able to take advantage of less jaded, less media-savvy, more credulous times. To even approach its mischief and magic in 2018 feels like a triumph of imagination. It also feels like a vindication of the idea that in the right hands, TV still has the capacity to surprise, disconcert and delight.