‘Zero Day’ Star Lizzy Caplan on That Big Finale Twist, Sparring With Robert De Niro and the Enduring Legacy of ‘Mean Girls’

SPOILER ALERT: This interview contains spoilers from all six episodes of “Zero Day,” now streaming on Netflix.

Lizzy Caplan always knew that her character, Congresswoman and former First Daughter Alexandra Mullen, was behind the catastrophic cyberattack that incited the existential and moral panic that runs through “Zero Day.” It’s a plot twist that comes in the early minutes of the finale of Netflix’s latest political thriller, which stars Robert De Niro (in his first major TV role) as President Robert Mullen, an aging, populist former leader who comes out of retirement to run a commission tasked with investigating the devastating nationwide outage.

As far as when she found out about her character’s villainy, she says: “I think it was probably before I read the scripts. I may not have been as aware of the magnitude of her role in it. Maybe I thought there were going to be other people who were involved, but I didn’t realize how much of it was going to be Alex.”

In a heated confrontation with her father inside her apartment, Alex comes clean about how the Zero Day attack came from within the highest levels of government — and how it all went terribly wrong. As it turns out, Richard Dreyer (Matthew Modine), the current Speaker of the House, had teamed up with tech billionaire Monica Kidder (Gaby Hoffmann) to orchestrate a plot against the sitting government of President Evelyn Mitchell (Angela Bassett). Alex had become part of the insurgency, fed up with the amount of political infighting that was preventing vital legislation from being passed.

“In just one minute, [Kidder] could remind everybody how vulnerable we are, how fragile we are, and that makes sense. It does,” Alex tells her father. “It makes sense that if you can remind people what’s really important, then maybe they’ll tune out all the noise and the bullshit and the lies, and we can go back to actually hearing each other. So we let it happen, because it made that point for us. It made it better than we ever could have made it, but I did not know that anybody was gonna die.”

Dreyer and even Mitchell are able to convince Robert to let Kidder alone take the fall for the cyberattack in his commission report, reasoning that it would be the most beneficial solution for all involved. But after Alex leaves her father a resignation note to read while delivering his report to the American public, Robert takes that opportunity to expose Dreyer’s involvement, even if that would implicate his daughter and tear his family apart even further.

Below, Caplan opens up about how she interpreted and justified Alex’s actions, her takeaways from working with onscreen father De Niro — and why she remains amazed by the enduring legacy of “Mean Girls.”

What did you find most intriguing about this fictional world that seems eerily similar to our current political climate?

The political aspects obviously are driving this story forward, and this is what the show is about: What would happen if something this awful happened to a country that’s this divided where we didn’t really know who to trust and we didn’t know who was telling the truth? And [what] if the truth became more subjective instead of what it’s always been? I found it all very compelling.

But what drew me in more was the interpersonal dynamics that were going on underneath all of it. Alex has a very complicated relationship with both of her parents, but primarily her father. There’s a lot of unresolved trauma that has occurred within the family — not only the overdose death of her brother, but the Valerie Whitesell [Connie Britton] character’s piece of it within their family. So there’s a lot of skeletons in the Mullen closet, and Alex has quite a lot of resentment towards her father for a lot of it and quite a lot of resentment towards her mother for sticking with her father.

So the challenge was maintaining that undercurrent of interpersonal drama beneath this super high-stakes, on-the-world-stage political drama, and every scene had both. There are very few straightforward scenes where characters are not keeping their cards close to their chest. Everybody is lying or telling half-truths the whole time in this show. That was the part that I found the most compelling, but also very challenging. I mean, there were 15 things going through Alex’s head in every beat of this show. She also was holding onto her own secrets on top of all of that, but it was a dream to get to explore all of that with the cast and with Lesli Linka Glatter, and I think it hopefully elevates it beyond just a straight political thriller.

So much of Alex’s adult life has been spent trying to step out of her father’s shadow. Midway through the season, Alex insists that she’s a congresswoman and not “daddy’s little girl,” and Speaker Dreyer reminds her that she’s both. What was your interpretation of Alex’s emotionally fraught relationship with Robert? Is she searching for love or approval from him? Does she want to be seen as different from him?

I think there’s a slew of things she thinks she wants, and then a few things that she actually needs from this relationship and is maybe not as aware of. She really wants her family to be honest about what happened to her brother, to own up to all of these defects of character. And she’s not going to get that from her parents, which she finds endlessly frustrating.

I think there’s a very universal theme that even though not many people can identify with being the daughter of a former president or growing up in the White House under that level of scrutiny from such a young age — that’s not a universal experience, obviously — I do think many people can relate to the idea that you think you know better than your parents, that your parents are drawing from an old playbook and they don’t get how things really work now in the modern age. That is Alex’s fatal flaw. She thinks that because she understands how the news cycle moves quicker, and there’s a social media element to politics now, she thinks that means she knows better than her father. I, Lizzy, really personally disagree with that, because what she doesn’t have is any of his experience and any of his wisdom, and she discounts that as less important than what she’s bringing to the table, and it leads her to make some very bad decisions.

All six scripts were written before the start of production, so you had a clear way to track Alex’s arc. How did you think about playing and teasing out her inner turmoil over the course of these episodes?

I think that it’s easy to want to play that you have a secret. That feels like maybe the right course of action when tackling something like this, but the reality is, I think people are better liars than we give them credit for. And when somebody is keeping this level of a secret, I think she’d be a very convincing liar, which she is. I’ll be interested to see, if you go back and watch it, if you can pick up on any little tells.

I do believe her intentions were noble. The results she was striving for, I can completely understand, but I wouldn’t have gone about it in that way. I think she’s immature, she’s sheltered. And even though, yes, she’s holding onto this massive secret and these massive lies, I think, at least for the first episodes, what’s allowing her to put one foot in front of the other is that she really believes in the cause that she’s fighting for. I think they probably all are fighting for the same cause. She just goes about it in a really questionable way.

All of Alex’s secrets spill out in a heated confrontation with her father in Episode 6. What do you remember from the process of shooting that pivotal scene, and what was it like for you to be able to spar with De Niro in that way?

Very intimidating. That was the scene that I was the most nervous about, for sure. I just kept thinking, if I can just get to the other side of that scene, I can breathe a little easier. We shot it all day. It was a very, very long day. It was totally exhausting. I don’t know if we all felt confident that we got it. I certainly will always question whether or not we got it at the end. I can’t imagine it’s any actor’s favorite day to have to maintain that level of intensity and emotion for 12 hours, but Bob was so generous, patient and amazing to work opposite. That was definitely not something that I don’t want to say that I expected, but it’s just not something that would’ve been necessary for somebody of his caliber to do. He doesn’t have to be as generous to other actors as he is. It’s pretty mind blowing, and I respect it so much.

Before meeting De Niro for the first time a couple years ago, you told Variety that you were “gonna let him lead” because he loomed so large in your brain and in your childhood that you just didn’t know what to expect from him. What do you remember from your initial meeting with him?

I think our first meeting was at his office, which is a pretty incredible place. The walls are lined with these photos of him with so many people, so many movie stills. It’s like a museum. But he was just kind, sweet, generous and genuine. It’s very obvious that even though he’s Robert De Niro, his priority is his family and that’s what drives him. I didn’t want to guess what he would be like, but he was so clearly just like a family man.

And yes, I was totally nervous to meet him, and I don’t really envy anybody in that position, to be that well-known for this many years. Living life as on that level of celebrity must have so many challenges. I think it would be very strange to have everybody look at you like, “I can’t believe this is happening to me,” every time you meet anybody. So I never lead with fangirling, because I am more interested in trying to understand the human being. But I also knew Jesse Plemons a bit, and he’s worked with Bob a bunch, and he told me he’s just a really good, decent guy — and this was the case.

The relationship between Alex and Jesse Plemons’ character Roger is, by design, difficult to define, but it’s clear from Alex’s reaction to his murder that he meant a lot to her and that she didn’t expect to lose someone so close to her as an indirect result of this cyberattack. How would you characterize their relationship? Were they just hooking up? Were they actually in love?

That was one of the positives that came out of that long six-month break [because of the strikes] that took us by surprise. We had gotten together at Lesli’s apartment — Lesli, Jesse, Eric and I — and we started talking about this relationship. We don’t really have that much real estate within the show. There’s very few scenes between the two of them, and there’s so much high stakes stuff going on around them that it was a challenge to try to figure out how we convey this really long history that these two have with one another. So we tried to fill those scenes with as many moments as we could that would convey just how long and how complicated and how intertwined their lives had been.

I think we also talked quite a bit about the death of Alex’s brother and how the three of them were probably always together and really tight. So losing Roger just compounds the anguish over losing her brother. These were her people. The spotlight was shining so brightly on them since they were children, so they found this group of people where they could act out and misbehave and be real kids together. I think both Alex and Roger’s character have a lot of demons, drugs, secrets, so we just built this backstory of what they had been through together, and we tried to pepper little mentions of it within the scenes just to try to give it this level of richness in very, very few minutes of camera time together.

How did you want to play out the aftermath of Roger’s death from Alex’s perspective?

I think by the time he dies, the wheels are really starting to come off. The plan has gone so sideways that the only way she can continue putting one foot in front of the other is to keep her eye on the prize, which was the end result that she was hoping for. I think it probably hits her a bit in the conversation with her dad when things finally come out. But I think, if anything, she just doesn’t have the bandwidth to process Roger’s death in any healthy way. She’s not giving herself time to grieve. She’s just barreling forward and probably trying to sidestep the feelings that are coming up not only about Roger, but about her brother and her own part in it.

You’ve personally gone from strength to strength in three very different shows: “Fleishman Is in Trouble,” “Fatal Attraction” and now “Zero Day.” I think it’s fair to say the “Caplanaissance” is on.

I’ve never heard that! If I hear it from a second person, I’ll maybe start to believe that you didn’t just make that up right now.

Well, I’ve just coined the term, so someone else can use it now. You’ve openly talked about how a lot of the misfit, left-of-center characters that defined your early body of work weren’t necessarily the people who were getting the really juicy leading roles, but we seem to have arrived at a cultural moment where those kinds of women have become a lot more normalized.

I think what you said is true. The culture and the TV and film landscape has changed so dramatically that when I was first starting out, the left-of-center characters were never the main protagonist, and they weren’t the roles people wanted. People wanted to be the “main girl,” and I was always drawn to those more misfit characters. But it was also frustrating because you never were driving the story more often than not. You never would’ve seen a show [like] “Wednesday” back when I was 19 or whatever.

So I do think that the culture itself is changing, but also, as you get older, I think the roles for women in television have always been the richest. We were just talking earlier about “The Sopranos” — Carmela Soprano is one of the greatest female characters of all time, so complicated. So there’s always been a place for TV, and I always have and will continue to run towards those roles. They’re the only ones that really hold my interest. And of course now, it’s just like a luck of circumstance, I guess, that the shows are now focusing on those messy, complicated, fractured protagonists.

Last year marked the 20-year anniversary of “Mean Girls.” When you look back on that film, what stands out to you? And did you have any say in Janis’ Goth look that seems to have stood the test of time?

I didn’t have much say in the look. Maybe I weighed in on flat-ironing certain parts of my weird, ruined dyed black hair? But I look back on it so fondly. I spent many years afterwards trying to not distance myself, but I didn’t want to be pigeonholed as that character, and I fought really hard against that. Now, at this age, 20 years later, I feel like I accomplished that to a certain degree, and that’s now allowed me to really appreciate how special that movie is and how special it was to have been a part of it. As you said, each new generation seems to love it. In a way, it feels like a rite of passage for every young kid — certainly every girl and quite a few boys — so it does feel like a legacy now. It’s something that I’m just endlessly proud to have been a part of.

And even though the high school itself in that movie looks so different [from] high school now — there’s no screens, there’s no social media. That’s not an element of this story at all, which would absolutely be an element of this story now. It is [an element] in the remake and in the musical. So, how on earth does it resonate with kids who are in high school now, when their high school experience really doesn’t appear to resemble the high school experience from “Mean Girls”? I mean, the themes are universal. It was a great, great script. And yeah, there are going to be mean girls in every iteration of high school, even if it ends up being on the moon.

This interview has been edited and condensed.