The BBC mini-series "Sherlock" is likely the most highly anticipated television series on air. The fourth season, which has suffered several setbacks, isn't set to premiere until 2017. Nonetheless, fans are eager to learn what's going to happen during the upcoming season.

The upcoming season, which will star Benedict Cumberbatch as Sherlock Holmes, Martin Freeman as Dr. John Watson and Mark Gatiss as Sherlock's brother Mycroft Holmes, is set to be filmed during the spring 2016 following the televised broadcast of the Victorian era standalone episode, set to air on Christmas day 2015. The Christmas special will be based on the story "The Adventure of the Blue Carbuncle," written, of course, by Sir Arthur Conan Doyle.

During the third season of the series, fan favorite Irene Adler (Lara Pulver) was decidedly absent, with the exception of her appearance during a hallucination during a single episode. However, if rumors are correct, fans might see the femme fatale return as a series regular.

"I honestly don't know," Pulver teased about a possible Irene Adler return. "She's only in one book and Steven [Moffat] and Mark Gatiss are big Conan Doyle fans."

Show creator Steven Moffat has said that the return of Adler is not "impossible, because she's still alive and out there.

"But I was really, really pleased with [Season 2 episode] 'A Scandal in Belgravia,' and that sense of longing between those two characters," said Moffat. "The question is, can you do it again without making it less good? Are sequels ever as good? Do you really make more money or do you debase the coinage? If we had as good a story as 'Scandal' and somewhere else to take them, we'd do it again."

Whether or not Adler returns, the upcoming season promises to be darker and one of consequences, where "chickens comes home to roost," according to Moffat. There will be great fun, but things will come back to bite Sherlock and others.

Likely, something devastating will happen, including the death of another major character. Many fans suspect that Mary Watson will presumably die because she died in the Sherlock series. However, the show is known for playing fast and loose with the original stories. That said, whatever's in store for team Sherlock, it'll likely be heartbreaking.

"The story of Sherlock Holmes isn't Sherlock vs. a criminal mastermind. It just isn't," said Steven Moffat in interview with Entertainment Weekly.

"We have a plan to top it. And I do think our plan is devastating. We've practically reduced our cast to tears telling them the plan ... we're probably more excited that we've ever been about Sherlock."

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