The fourth season of 'Sherlock' is finally on the way, even if we'll have to wait until next year to see it. We've been promised that Holmes will face demons from his past and his faithful companion Dr. Watson will have the responsibility of fatherhood on his shoulders this time.

Benedict Cumberbatch and Martin Freeman in SherlockBenedict Cumberbatch and Martin Freeman are back in 'Sherlock' series 4

We're still frustratingly oblivious to any real details on the forthcoming 3-episode series, and creators Steven Moffat and Mark Gatiss have done well in tying up loose ends in New Year's Day BBC special 'The Abominable Bride' to avoid any obvious speculation. That won't stop the die-hard fans though.

To recap, 'Sherlock' series 3 ended with Holmes' (Benedict Cumberbatch) brother Mycroft (Mark Gatiss) sending him on a suicide mission overseas in payment for his deadly crimes. Jim Moriarty (Andrew Scott) is apparently dead after shooting himself in the head in an attempt to force Holmes to commit suicide, and Dr. Watson (Martin Freeman) and his wife Mary (Amanda Abbington) are pregnant with their first child. Oh yeah, and just as Holmes is about to get on the plane out of the country, Moriarty's face is broadcast all over London saying: 'Did you miss me?' 'The Abomindable Bride' special elaborated on that ending, as Holmes goes into his mind palace to solve a Victorian case of an apparent suicide similar to Moriarity's. He manages, but then ultimately decides that Moriarity is definitely dead after all, and he's just left a trail of torment in his wake.

Martin Freeman and Benedict Cumberbatch in 'The Abominable Bride''The Abominable Bride' was set in Victorian London

As well as Cumberbatch, Freeman, Gatiss and Abbington, 'Sherlock' series 4 sees the return of Una Stubbs as 221B Baker Street landlady Mrs. Hudson, Rupert Graves as the long-suffering DI Lestrade and Louise Brealey as the coy pathologist Molly Hooper, though there's no word yet on whether or not we can expect an appearance from Holmes' number one nemesis (not his arch-enemy, that's still Mycroft) Moriarty.

More: The Abomindable Bride earns international success

Of course, it's very possible that Moriarty will make a comeback even if Holmes denies such a thing. But it's also arguably time for a new villain, given that the show appears to be signed on for yet another season after the next at the very least, and who knows how many after that?

Sherlock castAll the main cast are set to return [L-R] Louise Brealey, Amanda Abbington, Martin Freeman, Benedict Cumberbatch, Rupert Graves and Una Stubbs

Moffat and Gatiss revealed the official synopsis for series 4 in a statement: 'Ghosts of the past are rising in the lives of Sherlock Holmes and John Watson bringing adventure, romance and terror in their wake. This is the story we've been telling from the beginning. A story about to reach its climax...'

'Ghosts of the past' could be referring to Moriarty of course, though there are other mysterious faces that could return to shake things up a bit. What about the morally questionable dominatrix Irene Adler (Lara Pulver), who Holmes secretly rescued from terrorists in Pakistan? Could she be making a reappearance?

Whatever the case, we'll definitely find out next year, with much speculation that the first episode is very likely to air on New Year's Day again. Plus, it will mark the first time ever a 'Sherlock' episode has been directed by a woman as Rachel Talalay ('Doctor Who', 'The Flash' and 'The Wind In The Willows') signs on to helm the opening show.