Andrew Scott poses for photographers on the red carpet at the world premiere of the new James Bond 007 film "Spectre" at the Royal Albert Hall in London, Britain, October 26, 2015. Reuters/Luke MacGregor

Fans around the world recently had their fill of Sherlock Holmes in the “Sherlock” special episode that aired on Jan. 1. Now, they will have to wait till early 2017, to watch the three episodes of "Sherlock" Season 4, which is scheduled to begin filming in spring.

In “Sherlock” special episode, titled “The Abominable Bride,” Sherlock Holmes (Benedict Cumberbatch) travelled back in time, 19th century, to solve the mystery of a dead woman coming back to life. However, it was not a one-off special episode of "Sherlock," as it tied neatly to the ending of Season 3 as well as serving as a cliffhanger for “Sherlock” Season 4.

The one big question on the mind of every fan is whether Moriarty (Andrew Scott) will return, and if he returns, how will he return. He blew his brains out at the end of "Sherlock" Season 2. However, at the end of “Sherlock” Season 3 his face appeared across TV channels in England, asking “Miss me?” Sherlock insisted at the end of the special episode that no one can survive after blowing one’s brains out, but he also added: “Moriarty is dead, no question. But more importantly, I know exactly what he’s going to do next.”

There are four serious fan theories doing the rounds on the Internet. One is that Moriarty faked his death, like Sherlock, and that his gun was not loaded. This theory suggests there could have been a squib in Moriarty's collar making his death appear bloody. The second Moriarty theory claims that Sherlock had planned the entire thing with Moriarty himself.

A third theory suggests that Moriarty's face asking "miss me?" on every screen in England was faked by either Mycroft, who has adequate resources to do so, or Sherlock himself, to facilitate his return to England. This theory concludes that Jim Moriarty is indeed dead.

The fourth theory, the most interesting one, suggests Andrew Scott is not the actual Moriarty, but an actor pretending to be him. It also suggests that Moriarty may not be a single individual, but an organisation of people bent on making Sherlock’s life difficult.

The last theory can be a possibility, as in “The Abominable Bride,” Sherlock discovers that the actual ghost bride had not only faked her death once and then committed suicide for real, but there is an underground organisation of women who dress-up like the titular bride to terrorise and punish men who ruin women’s lives.

Well, Moriarty may not have such a morally righteous purpose, though he might as well be, like in the New Year special, an idea behind an organisation, which is targeting Sherlock.

Another interesting fan theory on Reddit postulates that Moriarty may be Sherlock’s split personality. However, no actual plot details have been announced yet. So, such theories are only speculations as of now.

If none of these prove true, Moriarty is still locked inside Sherlock’s mind palace and is likely to keep haunting him forever. Scott might return in flashback scenes.

Like Sherlock himself, series creator Steven Moffat also confirmed in an interview to Entertainment Weekly that Moriarty is indeed dead and has not survived his suicide.

“The story of Sherlock Holmes isn’t Sherlock vs. a criminal mastermind. It just isn’t," Moffat said. "So we wanted to have a huge story for 'The Final Problem,' but kill him… we knew what we wanted the consequences of that moment to be.”

Those consequences are perhaps what’s exactly in store for Sherlock to face once "Sherlock" Season 4 premieres in 2017. Moffat, while offering hints as to what “Sherlock” Season 4 will be about, had said that it’s going to be about “consequences.”

“It’s dark in some ways—obviously it’s great fun and a Sherlock Holmes romp and all that -- but there’s a sense of… things… coming back to bite you,” Moffat said. "It’s not a safe, sensible way to live. It’s hilarious and exhilarating some days, but some days it’s going to be bloody frightening.”

“Sherlock” Season 4 is also going to be more serialised, according to Moffat: “It will be three stand-alone films, 90 minutes each, and an ongoing mystery, as there sort of always is.”

The writer also said in the interview that "Sherlock" Season 4, or “series” as it is called in England, is also to be more emotional and intense than the preceding ones.

Moffat also added that fans will be “desperate for series 5,” after watching “Sherlock” Season 4. “We’re certainly going to put them through the mill,” he said about viewers. He added that “Sherlock” Season 4 will be a “tougher series.”

Another interesting update came from co-writer Mark Gatiss, who plays Mycroft Holmes on "Sherlock," who tweeted an image of Jabez Wilson’s pawnshop in February 2015 with the caption: “We Gingers must stick together…#Sherlock.”

Jabez Wilson is a character that was introduced in Arthur Conan Doyle’s story “The Red Headed League,” which might be the focus of one of the episodes in “Sherlock” Season 4.

Meanwhile, there’s also sad news awaiting fans -- if there are any -- of Amanda Abbington’s Mary Morstan. Actor Martin Freeman, who plays Dr John Watson, previously suggested that Mary could be killed off “at some point” in line with Conan Doyle’s stories.

“While we play fast and loose with the original stories, we generally follow the trajectory of what Conan Doyle did,” Freeman had told The Telegraph. “So he [Watson] gets married and then Mary dies -- so at some point presumably she’ll die.”

In Conan Doyle's storyline, she died at an unspecified point between “The Final Problem” and “The Adventure of the Empty House,” and her passing is mentioned briefly by Holmes in the latter. However, “Sherlock” Season 3 saw John and Mary expecting a baby. So, perhaps Mary will not be killed-off just yet.