We know whodunit — the question is, whydunit?

That’s a formula “The Sinner” has crafted to tremendous success. The first season of USA’s limited series scored with viewers, and landed Jessica Biel an Emmy nomination for her starring role. In Season 2, Carrie Coon steps into the spotlight as the enigmatic Vera, a woman who leads a cult-like community and the mother of a boy who has committed two heinous murders.

Everything isn’t what it seems, Coon promises. “[Showrunner] Derek Simonds has all these twists up his very well-tailored sleeves,” she reveals.

The day after shooting wrapped, Coon — a new mother herself — talked with Variety about why she’s drawn to mysterious characters, her biggest fear, and why she thinks cults hold so much appeal for people.

What made you want to sign on for the role?

I was just postpartum when [my husband] Tracy [Letts] got the call to play Jack, and it was probably about a week or two weeks later that I got the call to play Vera. Tracy had already decided to say yes because he’s worked with [executive producer] Antonio Campos before and he was very impressed by Derek’s presentation when they had a phone call about the show. And we really loved Season 1. We just thought it was really smart and some of the character work and the choices that weren’t necessarily plot-driven. And the idea that it was a whydunnit, it was a bit of a twist on the genre. So I said, what the heck, we’re all going to go to New York together! I thought it was I going to come to New York and hang out with my baby and see all of our friends. And as it turns out, I worked 14-hour days. Not the summer I was expecting.

What did it mean to you to be on the same project with your husband?

It’s funny that it’s become this pitch tool for people when they come to us. They’re like, “…and Tracy will play the uncle and Carrie could play the lunch lady.” I mean, everyone is now coming to us in tandem! I think the people who want to work with us try to seduce us by offering our partner a part which I guess is a benefit of having our careers dovetailing in this unusual way where my husband has this film career in his 50s and I’m having this career in my 30s and we just happened to be married. We’re very, very lucky. I wish I could work with him, actually work with him, right? Because I think he’s so tremendous. I guess I’ll have to settle for our work in the theater because even in “The Post,” we just walked by each other in a room.

How much did you know about Vera going into it? Did Derek lay out the whole arc of the season for you?

They hadn’t, quite. Derek had not quite solved the ending, but they had the rough arc of the way Vera and Ambrose [Bill Pullman] would ultimately interact. And what was fascinating about it is Vera is not just purely the antagonist. She’s the protagonist as well. In some ways she’s the victim of the circumstances. Her son [Julian, played by Elisha Henig] has committed this crime and now she has to deal with these bureaucratic machines that she’s been operating outside of for a long time. She needs an ally and Ambrose is her ally, but he’s also connected to the very institutions that are threatening her. It’s an odd position to be in because it’s not as though Vera is the evil villain, though I think some people believe that she is. I don’t think of her that way. She shares some qualities with Nora [from “The Leftovers”], so I knew I was going to have to find a way to play similar energy and find a new way of playing it because nobody wants to see you make all the same faces. I always live in horror of the Carrie Coon montage where they just cut together my scared face and I’m exposed as a hack and nobody hires you ever again. That’s my nightmare. I’ll just find something else to do. [Laughs.]

But you do have a knack for playing these ambiguous characters.

Most of all, I’m not afraid of ambiguity and I don’t care about being liked. A real human being is more complicated than that. I have love/hate relationships with most of the people in my life. Any family member you have, you have a love/hate relationship with them. I feel that good characters, if they’re written well and they’re full human beings, they’ll be that way too. And people are not so solvable. I find people very mysterious and their motivations for things, particularly right now, are very mysterious. It’s interesting because we live in a culture where everything is very polarized and everything feels very black and white. “The Sinner” very satisfyingly dabbles in the gray areas in a way that I find reflects real life even though it’s also a thrilling whydunit with some sensational twists.

True, we know who committed the crime from the first scene. So it’s just a matter of finding more narrative depth from there.

Exactly. We’re often quick to ascribe motivations to people’s actions without knowing all the circumstances. And particularly our justice system is flawed, it doesn’t always work. I think it’s interesting that this series concerns itself with the complexity of one’s motivation and all of the factors that influence the way we behave in a time when everything gets boiled down to the simplest common denominator on the internet, when in reality, most of the issues we’re struggling with in our country even are much more complicated than that. There aren’t easy answers and you can’t use blunt instruments to solve these problems.

So what do you think motivates Vera? What’s her guiding principle?

I think she’s a highly principled leader who believes that she’s offering the world a type of psychological work that creates integrated human beings and she believes that’s the future of humanity, but in fact reducing human actions to binary good and bad, right and wrong is not helpful. Ultimately, it’s reductive and it doesn’t allow us to live fully inside of this spectrum of what humans are capable of. It puts us on this teeter totter, on the scale of good and bad, right and wrong, and that those are actually values that are determined by society, by our agreed upon rules in society, but humans are ultimately animals and capable of a wide spectrum of behavior. And maybe the challenging part about being human is that we decide what’s good and bad and if we were to let go of that, what would we be? Who could we be if we weren’t living in a binary structure? I think she believes that what she’s doing is powerful and could really change the world for the better. She just has her own weaknesses, her own flaws. So while she sees the value of the system she’s perpetuating, she doesn’t necessarily operate perfectly within it.

What would you consider her flaws?

Pride. I think ultimately she’s very proud and I think she also gets off on control. And so while she’s advocating a version of letting go, of openness and integration, in fact she is still holding onto power. She’s still holding onto the thrill of being in control of someone’s transformation. And if she wants to be successful, her ego can’t be a part of the work that she’s doing and she hasn’t quite evolved enough to let that go. And her son is her ultimate project. Her son is going to be a new man. That’s her life’s work and it backfires. But like any fraternity that hazes with you, you have to double down on your belief system, when you make a bad decision and you have to justify why you made that decision. You’re able to rationalize almost anything — not that I’m referencing our election. [Laughs.] No, no, not at all!

That makes her a very different kind of adversary or foil for Ambrose than Cora [Biel] was in the first season.

Yes, yes indeed. Because I think in Cora he recognizes similarity. Here’s someone who’s repressed something and Ambrose is operating in the world in the way someone who suppressing themselves might. He’s very closed off. He’s very inscrutable and I think he sees in Cora a mirror more than anything. And in Vera, it’s quite the opposite. What she’s advocating is radical presence and he’s not capable of that. He feels responsible for this boy. And I think that’s an interesting part of the story as well. Why? Why does he feel that he needs to be the advocate that the boy needs in the world? Why, why him? There’s something about their storylines that connects them emotionally.

It’s becoming very much a tug of war for the boy.

Yeah. Right. Exactly. Yes, yes, yes.

It’s such an intense show to be working on. How do you get in and out of that headspace?

It’s funny, this question comes up a lot about, you know, whether or not you can. It’s hard to come down after shooting, but frankly TV moves so quickly. There’s always one more scene on the schedule than you’re actually physically able to shoot. You’re just so exhausted. I always find that as an actress we’re often asked to achieve emotional peaks on screen and do it over and over again. I talked a lot about this when it came to “The Leftovers,” and so in some ways you really have a genuine catharsis when you’re working on these shows. I get to leave it all on the field and go home quite refreshed because I had a really emotionally satisfying experience.

I know you’re not going to give anything away about the finale but do you think it’s a satisfying conclusion to the story?

I think by their very nature, the detective genre is generally pretty satisfying because the point of doing it is to solve the crime and the point of “The Sinner” is to identify the motivation for the crime that’s already essentially solved. And so I believe that they do a good job with their mission and so you get all the fun parts of a detective story, all the thrilling, exciting bits. And in addition to that you get this really interesting psychological journey, hopefully truthful psychological journey that feels real. I think we’ve gone to some pretty unusual places this season. I admire Derek taking some bold strokes at a genre people are really familiar with.

This season is also so much about motherhood, which must have been really resonant for you as a new mother. What other themes did you want to explore?

I guess I’m drawn to work that explores beliefs and spirituality because I’m always looking for how I’m supposed to live. I spent a week once researching the way I’m supposed to walk! It sounds prescriptive, but how to optimize walking is something that I obsessed over for a very long time. And I feel that way about making moral decisions in a world where I’m not a practicing Catholic anymore. I think I’ve discovered that oftentimes cults attract really intelligent people, people who are naturally seekers. And if someone is offering you enough tools that they make a difference in your life, it’s very easy for you to sign on for the long haul, hoping that what’s to come will deliver even better results for how to live, how to live more fully or more and morally or whatever it is you’re looking for. I appreciate that what Derek has done with “The Sinner” is he’s not making an evil cult show. I think we’ve seen the evil cult show a lot. I think “Wild, Wild Country” was really compelling for so many reasons, mainly because it doesn’t really end in a tragedy in the way those cult stories often do. That those people were able to accomplish some incredible things because there were extraordinarily talented people who had been drawn into that group and who were really looking to live in this utopia.

There might be something to the idea of living in this community that we’re missing in our increasingly secular society and something will rush to fill that void if there’s a void. We’ve seen some of the things that rush to fill that void and there they can be really terrifying and dangerous, but maybe there’s also some beauty there too. We’re living more apart than we ever have and technology has closed up some gaps, but it also creates distance and I think we’re going to see a lot of people turning to communities like Mosswood to reconnect. This might just be a little foreshadowing for the future.