There's an Inside No.9 episode that was never aired on television

For almost a decade, Reece Shearsmith and Steve Pemberton have sucked fans into their sinister Inside No.9 world.

And their most recent disturbing offering left some viewers 'traumatised' after witnessing a contestant's head explode during Lee Mack's 'new game show'. Check it out for yourself:

It's one of a seemingly endless line of episodes that have stayed with fans long after the credits finished rolling.

But did you know that there's an ep that never aired on television, and what's more, it starred neither of its creators.

Back in 2014, with the first season in full swing, the BBC released a special 'web-only' instalment called 'The Inventors'.

The interactive episode, which only lasts about 12 minutes, centred on two brothers, Andy and Dennis, played by Tom Verrall and Dan Skinner, who've struggled to cope since their mum died in the Great Storm of 1987.

YouTube/BBC

And now, that their dad has also shuffled off this mortal coil, Dennis suggests it's time to sell their flat.

Andy, however, has other ideas, and as the episode goes on, secrets start to unravel.

Viewers who managed to catch it online were able to choose how the story went, with each scene played out in a series of photographs with characters' voices overlayed.

Speaking at the time of its release, BBC producer Jon Aird said: "We wanted to explore new ways of telling stories digitally for Inside No.9, and the use of cinemagraphs allowed us to do that in a very interesting way.

"Cinemagraphs are a modern take on the humble animated GIF and their looping animations have an eerie quality, making them perfect for the show and for 'The Inventors' story in particular... but you'll have to watch it to find out why."

YouTube/BBC

If like me, you missed it the first time round, I'm sorry to say that the interactive version is no longer available, but you can still watch it on YouTube.

And you're certainly not alone, as it turns out there were plenty of fans who didn't have a clue it existed until very recently.

"Inside No 9’s interactive digital episode 'The Inventors'! - wait, what? How have I missed this?" asked one viewer.

Once you've caught up with that, though, you can head right back to the beginning and watch the episode considered by many to be 'the darkest ever'.

It’s called ‘Sardines’ after a popular parlour game.

BBC

In the episode, which was first broadcast on 5 February 2014, a couple – played by Katherine Parkinson and Ben Willbond – hold a party at a family mansion, and decide to have a game of sardines.

If you’ve never played the game, it’s basically the same as hide-and-seek, but only one person hides and when you find them, you have to join them in their hiding place.

As things progress towards the big reveal at the end, there are secrets and revelations galore, including allegations of adultery, childhood sexual abuse, and all sorts of horrible stuff.

Honestly, it’s horrific.

But if you've not seen that either, we're not going to ruin the twist for you here.