“Beware the frumious bandersnatch,” wrote Lewis Carroll in Alice Through The Looking Glass. Well we can’t yet comment on its frumiosity, but we’re dubious that it’s something to avoid. Bandersnatch is a brand new “event” episode of Charlie Brooker’s Black Mirror. It arrives on Netflix tomorrow, heralded by this cryptic trailer that just crashed online.

David Slade is the director and Charlie Brooker the writer of the new episode, which revolves around a young programmer in the mid-1980s who begins to question reality as he adapts a sprawling fantasy novel into a video game. He soon faces “a mind-mangling challenge,” it says here.

There have been long episodes of Black Mirror before: Hated In The Nation was an hour-and-a-half. But this is the first special that’s arrived un-anchored to a broader series. And Bandersnatch is also significant in its nifty use of the possibilities of streaming technology. Rather than a “straight” episode, it’s a choose-your-own-adventure affair, with hours of footage allowing viewers to negotiate completely different viewing experiences and narrative outcomes. And of course, it also means you can watch it again and make your subsequent viewings completely different.

“You alone are in charge of what happens next,” reads the press release. “The journeys you go on are a direct result of your decisions. There are choices to be made, challenges to overcome, dangers to encounter and, as always in life (and Black Mirror), consequences to be had. Choosing wisely could lead to triumph while taking the wrong path could end in disaster — but who’s to say what’s “right” and “wrong,” anyway? And fret not because once one experience comes to a close, you can — and should! — go back and make a new choice, alter the path of your story and maybe even change its outcome.”