Get your tea and biscuits ready, because the cult TV mystery-drama Sherlock has made a devastating return for season four, with more intrigue, misdirection and tragedy than you can prod a pipe at.

The premiere, titled The Six Thatchers, leaves the viewer with little time to stop and breathe, let alone think.

The narrative moves at a cracking pace as personal revelations and tangential ‘mini-cases’ are woven into a deeper examination of Mary’s (Amanda Abbington) past – exposed in the previous season following her marriage to Dr John Watson (Martin Freeman) – culminating in a gut-wrenching conclusion.

Not our Sherlock! Cumberbatch sounds uncommitted to returning in future.

But the biggest shock of the season is delivered off screen in a recent interview with the lead actor.

Speaking with The Daily Mail’s Weekend magazine, Benedict Cumberbatch said: “We never say never on the show, but in the immediate future we all have things we want to crack on with, and we’ve made something very complete as it is. So I think we’ll just have to wait and see.”

So this could also be the last time we see Cumberbatch play everybody’s favourite high-functioning sociopathic detective.

The lengthy delay – three years, not counting the 2016 special The Abominable Bride – between seasons has been attributed to Cumberbatch’s ever-rising star, which has seen the actor perform in a number of blockbuster films, including The Hobbit, The Imitation Game and Doctor Strange, to name a few.

Cumberbatch and his wife Sophie Hunter also recently started a family, with the birth of their first Cumberbaby, Christopher, in 2015.

Considering the creative team is adamant that only Cumberbatch can fill the role of Sherlock Holmes, if we do see the actor in the future, we may need to wait a few more years for the next season.

* MILD SPOILERS AHEAD *

If history has taught us anything, it is that death will never keep a good villain down.

This season’s premiere picks up where the previous season ended: with Mycroft Holmes (Mark Gatiss) assembling his team to address the return of Professor Moriarty as Sherlock figures the event is part of the villain’s ‘posthumous game’ – the final(?) stage in his master plan, as it were.

Mycroft is back getting his brother, Sherlock, out of jams again.

Despite Watson’s rebuttals, Sherlock can’t help but see Moriarty’s machinations behind every event and face that comes his way, a subtle distraction from the bizarre cases of vandalism befalling a random group of people – all connected by their ownership of a similar item: a plaster bust of Margaret Thatcher.

As events unfold, what first seems like a series of unconnected crimes leads Sherlock down a dark path that draws in Mary and Watson; a storyline that echoes elements of the 2012 James Bond movie Skyfall.

Martin Freeman is back as Dr Watson. And he is dealing with some big life changes.

As The Six Thatchers reaches its crescendo, we are served a devastating loss; a moment when you will catch your breath and curse the show’s writers for taking such an endearing character from you. Perhaps keep a box of tissues next to your cup of tea for when the moment comes.

Speaking of spy movies, this episode offers a little more action than the series is usually known for – a plethora of guns and even a flash-bang grenade – which could easily be passed off as producers pandering to a wider audience, but in truth actually serves the story well, adding a little modern espionage flavour to the whole ordeal.

Of course, don’t think the case of Moriarty is going to be neatly wrapped up in this one episode. We likely have the rest of the season to enjoy that evergreen narrative.

Watch Sherlock right now, exclusively on Stan.