When Mickey Sumner stepped foot back on the Snowpiercer set in October 2020, seven months after the production of the show had been shuttered due to the coronavirus pandemic, it was with a mix of fear and excitement. Prior to the lockdown in spring, eight episodes of the second season had been filmed and work had just started on the final two episodes when, in a shift that felt ripped straight out of the post-apocalyptic series, the entire world came to an abrupt, gear-grinding halt.

“We had started episodes nine and ten, but we had just never completed them. So then in October, we came back for two weeks and finished the season,” she tells MTV News over the phone from her home in British Columbia. The 37-year-old actress, known for her spellbinding performances in Frances Ha and Low Winter Sun, is currently on day nine or 10 — she’s not entirely sure — of quarantine before she begins filming the third season of Snowpiercer, which was renewed before the previous installment could air. Despite living in isolation, she’s not lonely or bored because her 4-year-old son keeps her on her toes. Nonetheless, Sumner was excited to return to set, in part because leaving the season unfinished “had been kind of hanging over us all.”

Based on the graphic novel Le Transperceneige and director Bong Joon-ho’s 2013 film of the same name, the television adaptation of Snowpiercer is set seven years after an experiment to prevent climate change goes wrong and transforms the world into a sprawling arctic tundra. Survivors ride a 1,001-car train segmented by class that must continuously circle the globe at high speeds to stay functional and keep its passengers alive. Sumner plays Bess Till, a punchy brakeman with a hidden soft side, who is tasked with keeping order within the lower-tier cabins. It’s there she meets Layton (Daveed Diggs) and joins him on his journey as he inspires a revolution on board.

Now, in its second season, Till is forced to adapt to a new set of challenges as the passengers fight for power. Battling PTSD in the aftermath of a blood-soaked revolt, she’s assigned the role of train detective and thrown headfirst into the deep end on her first case to uncover the mastermind behind a slew of vicious attacks on civilians. Wracked with emotional pain, loneliness, and a crisis of identity, Till leans into the companionship and guidance of Pastor Logan (Bryan Terrell Clark), but a breakthrough in the case may have her questioning everything she knows about her revolutionary companions. Much will be revealed in tonight’s episode, and ahead of it, Sumner lets MTV News into the mind and backstory of her awe-inspiring character.

MTV News: When did you first know you wanted to be an actor?

Sumner: I grew up watching my mom [Trudie Styler] on stage, in movies, on film sets, and I was always really fascinated by that life. I always thought I wanted to be behind the camera; I really was interested in costumes. My godmother is Colleen Atwood, who is a costume designer, so I spent a lot of summers interning for her and learning costumes. For college, I went to Parsons School of Design and studied painting, but what was really great was that it was in New York City. I got to meet all of these kids who went to New York University, Bard, and Columbia who were all making things. I fell into that crowd, and they’d asked me to help out and make a short film over the weekend and I got hooked that way. I started taking acting classes at night with this amazing woman Sondra Lee, who is one of the greats. She really got me on my feet in theater and told me that I was good. And I felt like, OK, this is what I want to do, so I graduated with a degree in art and became an actress.

MTV News: You mentioned that you were initially interested in costume design growing up. Has that training been reflected in Till’s outfits throughout Snowpiercer?

Sumner: Aesthetics, composition, fabrics, and just the general look of every character I play is so vital for me to build a layered character. I take that really seriously and work out my hairstyle, my shoes, my socks. I really like to layer up — even my underwear needs to be right for the character in order to feel her! We’re really lucky on Snowpiercer to work with such a talented costume department that really respects and appreciates my process. It was a collaboration in finding the right coat for her in Season 2 when she becomes a detective. It was really important to me how it swings when I walk down the corridor and how the collar pops, just these very small details that maybe no one notices.

MTV News: What was it about the role of Till that initially drew you to the character?

Sumner: I auditioned four years ago and not very much was told about Till. It was very secretive. There was no script — all I knew was that she was this sort of cop figure. She was tough with some underlying vulnerability. That was the breakdown, which immediately felt interesting to me; a sort of kickass, badass woman who might seem one way on the outside and then has some softer facets. I think, as an actor, you’re always looking for that contradiction.

MTV News: That contradiction is one of my favorite things about Till. She can be brave when she’s storming the train with Layton in the first season, but she can also be emotionally vulnerable when she opens up about her fears. How did you work to balance both sides of the character?

Sumner: I think the script really dictates it in a beautiful way. It’s the homework of the actor to make sure you know your backstory, your weaknesses, so that even when you’re trying to be tough or have a fight scene, there are those places that you can see the cracks. The PTSD of Bess Till in Season 2 is actually something that was quite close to me. I’ve actually been suffering PTSD after the birth of my child. It’s something I’ve been working through and so it felt, in one way, quite healing to be able to go there in character. Even just talking about it feels vulnerable. I love that about art — you can channel these things that happen in your life and put them somewhere creative.

MTV News: So there are aspects of her character that especially resonate with you?

Sumner: A lot! When I was in high school, everyone said that people were afraid of me because I had this walk and was very serious. I didn’t let my guard down and I didn’t trust a lot of people. Then, when you get to know me, there’s a softer, more lighthearted place.

MTV News: When Layton gives Till the role of train detective at the beginning of the season, she’s almost reluctant to take the opportunity. What does taking on the position represent for her?

Sumner: When we see her in those first two episodes, she’s reeling from the loss of life from the revolution and the loss of her identity as a brakeman that she’s given up She's also broken up with her love, Jinju, and that also came with a second-class cabin [on the train]. So she’s not only adrift romantically, but physically she’s sleeping on the bunks in the brakeman barracks and doesn’t really have a home. When she is given this job as a detective, she says: “I’ve seen enough bloodshed in my lifetime.” She doesn’t really want to go there, but she’s also a very dutiful person who understands the value of service. She’s very much willing to go with Layton and be whatever he needs her to be — she trusts him and wants to be part of his mission.

MTV News: Snowpiercer was greenlit for a third season ahead of the release of the second. How would you like to see Till continue to grow?

Sumner: I’m always interested in how a character transforms and learns. It’s important for me that something has shifted by the end of the scene. The amazing thing about TV is that you often start the season and the end of the season hasn’t even been written yet! As a control freak, I find it a bit stressful but also kind of exciting; you’re just sort of waiting to see what the writers have in store for you. As a character, I’m interested in where her trust lies now. Till is a romantic at heart who just really longs to love and be loved. I’m curious if that is going to play out this season. I don’t know — I’ve seen the first script and I can tell you there’s a lot of action!

MTV News: Despite Snowpiercer’s post-apocalyptic setting, at the heart of its story are aspects of society we deal with every day. What is it like to be part of a show that has these parallels?

Sumner: I feel like a broken record, but I keep saying that it’s not a futuristic, post-apocalyptic, sci-fi story. It’s the story of now. It’s an allegory of how our society plays out in these sort of insidious systems of greed, capitalism, and oppression. Who is serving who, and who is being sacrificed for the 1 percent to have a certain lifestyle? I think that it's a powerful story to really question the way we live and what structures we want to be part of, what structures we want to serve, and what structures we want to rebel against.

MTV News: Till always seems to have the option between doing what’s easy and doing what’s morally right. In the end, she always chooses what’s right. Where do you think this altruism comes from, even in the darkest of settings?

Sumner: In her heart, she’s always searching for how to be of service to the right thing. That probably came from childhood. But I think that somewhere in the seven years before Season 1 began, she lost her way and became part of the machine of oppression. I think that when she meets Layton he sees something in her and she feels seen by him; maybe subconsciously she realizes that there’s a way to redeem past behavior and change her path.

MTV News: I especially love the dynamic between Layton and Till. Over the last two seasons, they’ve become such a fantastic team and I feel like he may be the only person she can trust and rely on.

Sumner: I think so! She gave everything up for his mission and his vision because she really believed in him. I haven’t really talked about it before, but [before the events of Snowpiercer] she was a rookie cop from Detroit and he was a detective in Chicago. That understanding and the structure of the police department, where rookies are meant to look up to the detectives, was something I studied a lot before I started this show. When Till realizes that he’s a detective from the tail [of the train] it just tips her whole perspective on its head. She was part of a brutal regime where she was feeding these poor people in the back [of the train] cockroaches and she realizes this guy was someone she really should have been respecting. But I love working with Daveed, and Till would like to follow Daveed anywhere he would let her follow him.

MTV News: What do you hope fans take away from Till’s character arc?

Sumner: I think that if anyone is suffering from PTSD, I just hope they don’t feel alone and like they can get help. There is a real message in this season about who you are fighting for and what you are doing about the injustices that surround you every day. Can you stick up for your neighbor? Can you stick up for someone who is less privileged than you? Can you examine your own behavior and how you have benefited from systems of oppression and privilege?