In a recent interview, Co-Creator of Sherlock — Steven Moffat said, “I don’t know if people are attuned to the idea we might be spinning them deliberate red herrings.” This means that going into the fourth season of Sherlock, fans are more concerned than ever that their burning questions might not be answered satisfactorily, or, at all. After a triumphant first two seasons, the third season of Sherlock arguably spent more time poking fun at new mysteries than actually solving any existing ones. And while last year’s “The Abominable Bride” was a delicious tribute to the Victorian origins of the original characters, it also confused the concrete facts with the meta-fictional commentary. The more Sherlock dances with impossible, the more the show seems to create improbable solutions to dangling stories.

Debuting on January 1, the fourth season might end up being the very last run of the show. Meaning, the game is afoot and the pressure is on. While Sherlock Holmes delights in making the outrageous seems commonplace, there are still a few simple questions most fans are hoping to have answered.

Here are six lingering issues to consider as Sherlock Season 4 kicks off the new year.

Spoilers for Sherlock Seasons 1-3 ahead.

6. Mycroft’s Allegiances

Throughout the entire run of Sherlock, the allegiances of Mycroft Holmes have been shifty. In Season 2, he seems to be assisting, or at least, cooperating with Moriarty outright. In Season 3, he seems to have knowledge of events and situations which could have helped Sherlock on numerous occasions, and yet, he withheld them. Now, the trailers for Season 4 show Mrs. Hudson giving Mycroft a piece of her mind, calling him a “reptile.” This suggests Mycroft has done something awful and that in Season 4, figuring out where Mycroft stands is even murkier. And yet, if this is the finale season of Sherlock, some kind of peace — or explanation — needs to be created between the Holmes boys.

5. Did Moriarty Really Die?

In the Season 3 finale, Sherlock was brought back from exile specifically because Moriarty somehow sent a message from beyond the grave saying “Did You Miss Me?” The first obvious question is simply: Is this really Moriarty? Or some kind of trap he laid to take effect after his death? We saw Moriarty kill himself in “The Reichenbach Fall,” but would he really do that? Last year, the events of “The Abominable Bride” were revealed to be all taking place in Sherlock’s mind as a kind of mental exercise to figure out why and how Moriarty could return. At the very least, this season needs to explain the message from Moriarty, if not the fate of the evil criminal mastermind himself.

4. Mary’s Mysterious Past

We know Mary Watson (née Morstan) had a shady past prior to assuming her present identity. John Watson was given all of this clandestine information on a little flash drive, but chose not to peek at its contents. Still, the evil Charles Augustus Magnussen thought the information was damning enough to use as blackmail against Mary, John, and Sherlock, meaning there must have been something in there. Since Mary, John, and their newborn daughter are central to the new season, it stands to reason some unanswered questions about Mary’s past must come to light.

3. A Third Holmes Brother? (Or Sister?)

So far, Sherlock has made two references to the existence of a third sibling of Sherlock and Mycroft Holmes. In “The Empty Hearse,” when reminiscing about their childhood, Mycroft infers that he and another sibling weren’t sure about Sherlock when he was younger. In “His Last Vow,” Mycroft says, “You know what happened to the other one,” leading some fans to believe the show might acknowledge the apocryphal character of Sherrinford Holmes, who many fans have speculated could have existed in the original Conan Doyle canon. Some pre-Sherlock book fans even went so far as to suggest that Sherrinford assumed Sherlock’s identity after the events of “The Final Problem.” In the context of the Sherlock continuity, this would mean that the third Holmes sibling could be a character who we have already met. Moriarty has been a popular candidate among fans, but what if the secret Holmes wasn’t a man? What if Mary Watson is…really Sherlock’s sister!

2. Redbeard, Sherlock’s Dog

Sherlock remembers his dog in "His Last Vow."

The third season finale, “His Last Vow,” found Sherlock Holmes in his mind palace, revisiting memories of his childhood dog, Redbeard. Not found in any of the original Arthur Conan Doyle texts, Redbeard is a creation of the BBC show exclusively. So, what happened to Redbeard, and does it matter? And is it somehow connected with the possibly secret third Holmes sibling? Early promotional shots for Season 4 showed Sherlock with a dog, too, but it didn’t seem like it could have been Redbeard. Will Redbeard matter in the new season?

1. How Did Sherlock Do It?

Sherlock, right before the jump.

The cliffhanger from the second season of Sherlock was ultimately unresolved in the third season. While “The Empty Hearse” contained a lot of winks and nudges to various fan theories, and even saw Sherlock giving Anderson an “explanation” as to how he faked his death, there still isn’t a good or “real” answer. Other than Molly Hooper assisting Sherlock, there’s still pretty much nothing that we know definitively. If the fourth season does end up being the final outing for this incarnation of Sherlock Holmes, the fans will want to know exactly how he faked his death.

Sherlock debuts on January 1, 2017 on BBC One and Masterpiece Mystery on PBS.

Photos via PBS Masterpiece Mystery, BBC