Well, that's your lot. Ninety dizzying minutes of drug-addled, time-travelling chaos, and Sherlock is off our screens for another year - at least. Just in case January wasn't depressing enough already.

Despite the fact that the only literal plot development in 'The Abominable Bride' was that Sherlock got out of a plane, the episode left behind plenty of new threads for us to pick obsessively at until 2017. Here are seven of our biggest questions about series four…

1. What is Moriarty's next move?

"Moriarty is dead. More importantly, I know exactly what he's going to do next." A bold statement there from Sherlock, given that he's spent the last few hours tripping balls trying to work out whether there's any way Moriarty really could have returned from the grave. So Moriarty isn't alive, but he is back.

Before waking up with this new clarity, Sherlock had a dream in which he re-imagined his Reichenbach Fall with a new ending: John saves him, and pushes Moriarty over the cliff to his death. Are there any clues here to Moriarty's next move? The answer might lie in this exchange:

Moriarty: "That's not fair, there's two of you."

John: "There's always two of us. Don't you read The Strand?"

It's the fact that Sherlock doesn't work alone that saves him, but what if Moriarty has a partner too? Since everything we saw in 'The Abominable Bride' was Sherlock trying to work out Moriarty's plan in his own mind, maybe this dream sequence was his realisation that there are "two of Moriarty" too. Is Sebastian Moran - Moriarty's right-hand man who got such weirdly short shrift in series three - about to make a return?

2. Have we seen the last of Victorian Sherlock?

However you feel about 'The Abominable Bride' and its twist, it's hard to deny that it robbed us of the genuine, full-blooded Victorian Holmes story we were promised. The 1895 world we saw was only a creation of Sherlock's mind palace, but that's not to say we couldn't return to it down the line, now that the device has been established.

Given how effortlessly Benedict Cumberbatch and Martin Freeman segued into their Victorian selves, it would be a shame never to see their Holmes and Watson put to work on a real mystery. And let's not forget that epilogue, which finds the Victorian Holmes and Watson talking as though it's the 21st century timeline that's a figment of their imagination.

BBC

3. Is Mycroft going to die?

Exhibit A: The scene between obese Victorian Mycroft and Sherlock in which they discuss how long Mycroft has to live, and talk about his "gambling with his own life". True, it's a nod to the original novels, in which Mycroft was massively obese. But it's too specific, and frankly too bleak, to dismiss as comic relief, especially because it's happening in Sherlock's head. Given his powers of deduction, has Sherlock subconsciously picked up on the fact that his brother is dying?

Exhibit B: Mycroft has been uncharacteristically sentimental both in this episode and in 'His Last Vow', and more openly concerned for Sherlock than ever. Remember the way Mark Gatiss delivered the line "Sherlock, promise me..." - it felt very distinctly like there's something more going on with Mycroft.

Exhibit C: "Doctor Watson? Look after him. Please." Ditto this line, which was downright ominous.

4. Is Mary going to die?

This one's been on the cards for much longer than Mycroft's maybe-demise, since Mary dies in the canon after several years of marriage to John. "While we play fast and loose with the original stories, we generally follow the trajectory of what Conan Doyle did," Freeman told The Telegraph last year. "So [Watson] gets married, and then Mary dies - so at some point presumably she'll die."

Moffat and Gatiss have promised that series four will be dark and somewhat tragic, but the double whammy of both Mycroft and Mary dying would surely be too much - especially with Mary still pregnant. Then again, in Sherlock's mind Mary was working for Mycroft, so maybe series four will see their fates align.

5. What's the significance of Redbeard?

We know from 'His Last Vow' that Redbeard's the name of Sherlock's beloved childhood dog who was put down. But is that all there is to it?

While Sherlock and John are waiting for Emelia Ricoletti's ghost to turn up at the Carmichaels' house, there's a blink-and-you'll-miss-it moment where you hear the sound of an approaching dog, and Sherlock murmurs "Redbeard?" Then there's Mycroft's mysterious notebook, as pictured above, where the name is prominent again.

While we're at it, what's the significance of "Vernet?" and "Scarlet Rolls" in Mycroft's notebook? Sherlock mentions in the canon that he's related to a French artist named Vernet, so maybe Mycroft's just digging into his ancestry. Or maybe it's a reference to Vernet's Syndrome, which suggests once again that Mycroft may be seriously ill.

BBC

6. What happened to the third Holmes brother?

Back in 'His Last Vow', Mycroft had a throwaway line that was easy to overlook amidst all the Moriarty excitement. "I'm not given to outbursts of brotherly compassion - you know what happened to the other one," he said, during the negotiations which ended in Sherlock being sent into exile. All the emphasis on the brothers' relationship in 'The Abominable Bride' has only made us wonder more about the other one.

7. Does Moriarty have a twin?

"It is never twins, Watson." Or... is it? It was speculated back when series three aired that Janine - Sherlock's short-lived and mistreated "girlfriend" - could be related to Moriarty, basically because they're both Irish and dark-haired. There wasn't much to back this theory up at the time, but given the lengthy 'twins' exchange in this episode and the brief reappearance of Janine, it's back on the table in a big way.

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