Jonny Lee Miller, Lucy Liu, Rhys Ifans Jonny Lee Miller, Lucy Liu, Rhys Ifans

Sherlock Holmes (Jonny Lee Miller) will have at least one last big mystery to solve before Elementary signs off for Season 2 — and this particular case could be life or death.

Mycroft Holmes (Rhys Ifans) has been somewhat of a mystery since making his first appearance earlier this season, and for good reason: The languid lout has been lying to his brother the whole time. It turns out, Mycroft has been working as an asset for MI-6, using his restaurants as a way to gather intel for Britain's secret intelligence agency.

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But, in another twist, Mycroft left MI-6 years ago, only forced to recently return to secretly protect his brother from prosecution after unknowingly helping a terrorist during his drug spiral in London. That being said, it seemed easy to fall in line with Sherlock's theory that Mycroft was being framed for the murder of an MI-6 analyst who had uncovered a mole within the agency. But what if Mycroft isn't being framed at all and actually is the mole? took that question and more to executive producer Rob Doherty to get the scoop.

Will Sherlock feel a sense of duty to help Mycroft because his brother apparently protected him by joining MI-6?
Rob Doherty:
Yeah, he absolutely feels an obligation first and foremost because Mycroft is family, but finding out what Mycroft did for him is going to hit him pretty profoundly.

How does their relationship change once this information is out there?
It's probably not a terribly big surprise, but that will come to light in the finale. Sherlock will find out that Mycroft made certain sacrifices for him. Those will land on him in a certain way. Sherlock is finding some respect for his brother. He's never really had much.

Sherlock and Joan (Lucy Liu) think Mycroft is being framed, but is there a chance that he really is the mole?
Sure. On our show? Yes. There is always a chance. I like Mycroft, so I don't know if that will be the final move we make, but absolutely. He's obviously done a very good job at keeping big secrets from Sherlock Holmes and that's no mean feat. Could there be others? Absolutely.

How will Sherlock be dealing with Joan's decision to move out?
Sherlock is struggling with it very obviously. What you'll see in the finale is someone who is really struggling to process the mere mention of it. He does not like change. He has settled into a very comfortable situation — or at least comfortable by his standards — in New York. He hates the idea of disruption. For Sherlock, so many different aspects of the way he lives his life are tied back to his sobriety. What could sound like a relatively small move can have much bigger ripple effects for someone like him. Canonically, we like the idea of Watson deciding it was time to move out and find new quarters.

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Sherlock hid those drugs in his library, so could Joan making this decision be the thing that pushes him over the edge?
Because Sherlock is sensitive to the degree that he is, absolutely. Seemingly small things can hit him very hard. For someone who is set in his ways to the degree that he is, it's difficult to wrap his head around this proposed change. When he secreted that little bag of heroin away, none of this was on the table. We still don't quite know what drove him to take it and stash it, but the possibility of Joan moving out is certainly not helping matters.

Mycroft is in a pretty dangerous position now, which could also send Sherlock over the edge. Should we be worried about death in the finale?
Yes. Be afraid, be very afraid. That is an absolute possibility. At different times in the episode to varying degrees, each person's life is in danger. I would say Mycroft finds himself in the very hottest water in the finale.

With all this deception in the air, could Joan and Mycroft's relationship ever really work?
It's tricky. There are a lot of factors going against them, not the least of which is that Sherlock is Mycroft's brother and Joan's partner. That's tough for any couple to overcome. That's a question we're looking to answer as the season wraps up. We'll have a pretty definitive answer to that.

Are you aiming for another close-ended finale or will you actually have some through-lines into next season?
We will tie up certain loose ends. It's not a proper cliff-hanger, but between Sherlock and Joan, some pretty drastic decisions will be made that will require correspondingly drastic changes to their lives. We're not going to leave anyone tied to a bomb or anything like that. It's more about their friendship and partnership, big changes coming and what that will mean as we start to dive into the work of Season 3. Where are Sherlock and Joan as we start the next year?

Do you think Mycroft is really the mole? Find out when Elementary's season finale airs on Thursday at 10/9c on CBS.

(Full disclosure: is owned by CBS.)