Spoiler Alert! This article contains spoilers for Stranger Things Season 5.

When Stranger Things Season 5, Episode 7 – The Lost Sister aired in 2017, the character of Kali – played by Danish actor Linnea Berthelsen – provoked a strong and often quite mixed reaction from fans. Appearing in a single, standalone episode, Kali nonetheless became one of the show’s most debated characters. Years later, her return in the final season invited audiences to reconsider not just the character herself, but the trauma, love, and intent that had always defined her. 

I sat down for a chat with Linnea, as she reflects on Kali’s journey, the intensity of fan response, and what it meant to return to a role that left such a lasting impression. Drawing on fan questions and her own reflections, this interview explores what Kali was always trying to protect – and why her story continues to strike such a chord.

What first drew you to acting, and when did it shift from something you enjoyed into something you wanted to pursue seriously?

I never acted as a child, and that’s really shaped how I approach the work. Acting has always felt like a job to me – structured and task-focused. I didn’t grow up with that childlike joy some actors talk about, but from the outset it was about what’s required of you and how you meet that.

I went backpacking on my own when I was 18, and in New York and Los Angeles I took my first acting classes. That’s when it clicked. I was drawn to building characters and creating something audiences can connect with from different angles. For me, it’s always about serving the story and the audience – being a vessel for what the character needs, rather than trying to get something personal out of it.

You grew up in Denmark and later trained in the UK. How did that move shape you personally and creatively as you were finding your voice as an actor?

I came to the UK to study because I really wanted that British training. That was always a dream of mine. There’s such a strong theatre tradition here, and the quality of voice coaching and classical training is incredible, so it was something I knew I wanted to immerse myself in.

Even after leaving drama school to do Stranger Things, I didn’t stop training. I sought out teachers I trusted and kept working with them, which has really shaped how I approach the craft. I genuinely love training, and I’ve been very lucky to find a small group of brilliant teachers early on. For as long as I’m lucky enough to do this work, I’d love to keep coming back to those teachers and continuing that training.

Before Stranger Things, you were working across short films and smaller projects. What did those early years teach you about the kinds of stories and characters you wanted to pursue?

Those early years were very raw and gritty. I was working mostly in Europe on no-budget projects, which meant everything felt stripped back and intense. That environment taught me less about specific stories or characters, and more about how I like to work.

It showed me that I’m drawn to an immersive way of working, and it really cemented my love for European cinema – the subtlety, the texture, and quieter forms of storytelling. Those instincts came directly from those early experiences.

When Stranger Things first came along, what did you actually know about Kali from the audition material, and how much of her did you have to invent for yourself?

Originally, the character wasn’t Kali at all – she was called Roman, and she was written as a 30-year-old white man. So it was very different to what she eventually became. What I took from that wasn’t the specifics of gender or age, but the energy and the dynamic they were looking for. It was always about who this character would be opposite Eleven.

When I approached the audition, I focused almost entirely on Millie’s performance and on building an interesting dynamic between them, rather than on revenge or backstory. I watched the first season, prepped intensely over a weekend, and tried lots of different versions until something clicked.

Even after the character changed and became Kali, I still related strongly to that original name, Roman. It felt quite neutral and helped me access the character in a way that was more about presence and relationship than labels. That foundation stayed with me throughout.

Ahead of the interview, I invited questions from the Stranger Things Facebook group, and a number of those appear here, with contributors credited.

Chloe Collins from the Facebook group asks what helped or inspired you most when developing Kali as a character. Did 1980s media, MK-ULTRA history, or research into trauma feed into how you approached her?

Thank you so much for that question, Chloe. 

Season 5 was very different from Season 2, because this time we knew so much more about who Kali is. For the final chapter, a huge part of my preparation was research. I went to the Imperial War Museum in London and studied the experiences of child Holocaust survivors, particularly children who had been experimented on. It was incredibly heavy, but it helped me understand a child’s relationship to trauma when that’s all they’ve ever known. I worked through that material closely with my coach and let it inform how she moves and exists in the world.

There was also a lightness I wanted Kali to have this season. When you accept that you’re going to die, you stop performing – there’s no one left to perform for. What’s left is something very raw and direct. At the core of it all, Kali has never experienced unconditional love and wants to feel worthy of it. By the end, she understands that Eleven can live on because she is loved. Kali’s love for Eleven is unconditional – it’s the only place she’s ever known it – and everything she does comes from that.

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Chloe Samantha asks what it was like working with Millie Bobby Brown, especially given how emotionally charged Kali and Eleven’s relationship is.

Millie is phenomenal. She’s an extraordinary actor, and what’s really interesting is that we work quite differently. She has this incredible ability to tap in and out of character with total precision, which is amazing to watch. I come from a place where I tend to stay much more inside the character, so that contrast actually created a really strong dynamic between us.

For the more intense scenes, especially the death scene, we were completely present with each other. It’s one of the strongest scenes I’ve ever done. We were both fully pulled into it, and I stayed in that emotional state for almost the entire day – it ended up being a very long shoot. That kind of work is only possible because of trust, and that relationship with Millie made it possible to go there and stay there.

When Season 2 aired, the response to Kali and that episode was intense and divisive. How aware were you of the reaction at the time, and how did you personally experience it?

I don’t really read much online, for better or worse. I tend to do the work, learn what I can from the experience, and then move on. I didn’t engage much with the reaction at the time, and for many years I just left it there.

More recently, I’ve noticed bits of it in passing, but I still don’t engage deeply. What always strikes me is how invested people become – how real it feels to them. On one level, you think, ‘It’s a character’, but on another, that intensity means people believe her. Matt and Ross [the Duffer brothers] always knew where the story was heading, and I trusted that. Seeing how passionate people still are just reminds me how powerful that connection is.

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Shane Guevara asks whether you enjoyed playing a character who challenged audience expectations so strongly.

Absolutely – that’s the best part. It’s exciting, especially on that scale, but it’s also nerve-wracking. You can’t really be afraid if you’re going to play characters like that. I think it’s necessary to understand why you’re doing it, though. You need to sit down with the writers and ask what the purpose is and what questions the character is meant to raise.

For me, Kali sits in a very philosophical space. She brings up ethical questions about what the ‘right’ thing to do actually is – ideas around morality, utilitarianism, and impossible choices. I find that kind of work really exciting. Those are the characters that stay with people, because they don’t give you easy answers.

Eric Buck asks whether, looking back now, you feel Kali was misunderstood, or whether the discomfort she caused was actually part of her purpose.

I don’t think Kali was ever meant to be straightforward. She’s designed to make people ask questions, and you can choose whether or not you want to engage with that. Was she misunderstood? I don’t know if that’s even the right word.

My job is to protect her, because I love her, and I see her as very human and very truthful. I’m not sure we need to fully understand her, or label her as good or bad. She’s just there, existing in that grey area, and I think that discomfort is part of what makes her interesting.

Cherish Nicole Martinez asks whether there was anything about Kali’s inner life or backstory that didn’t make it onto the screen that you wish viewers had understood better.

That’s a really, really good question – well done. I think it’s always easier if you get more time with a character, but it’s also a huge cast, and there are only so many places the story can go. I was actually very lucky to get the sense of closure that I did, and that Matt and Ross wanted to make that transition happen for her, so I’m not going to complain about that.

If anything, I think there could have been more exploration of Kali’s dynamics with some of the other characters, which might have clarified certain things. But ultimately, it’s Matt and Ross’s story to tell, and I really respect that.

George Hassard asks when you first heard about the possibility of returning for the final season, and how difficult it was keeping that secret.

It was about three years ago, which is a really long time to sit on something like that. I only told a handful of people – my parents needed to know, and a couple of close friends – but most people around me had absolutely no idea.

It was especially tricky because it involved a lot of wigs. Netflix provided them, and they were good wigs. My head was shaved on my very first day of principal photography, so for a long time I couldn’t really explain what was going on. Netflix were understandably worried it might be a giveaway, so I’d wear the wigs when I went home, and somehow it worked. A few friends genuinely didn’t notice at all!

Bethany Greaves and Maddy Williams ask: stepping back into Kali years later, how different did she feel to you as a character compared to Season 2?

That’s a really good question. I decided to treat her as a new character, because so much time had passed and her circumstances had completely changed. She still has that guardedness, but when you know you’re dying, something shifts – there’s a lightness that comes from letting go.

I approached her very precisely, really leaning into the script and what Matt and Ross were asking for. What carried over from Season 2 was her way of observing the world, but emotionally she felt different. Her world has become much smaller and more focused. There’s no one left to perform for, and everything centres on making things right with Eleven.

KJ Khan asks: Kali returns having been imprisoned and deeply traumatised. Did her imprisonment shape how you approached her in the final season?

Definitely. A lot of my preparation centred on understanding what it means to grow up in trauma when that’s all you’ve ever known. I read Always Remember Your Name by Tatiana and Andra Bucci, who were Holocaust survivors as children, and their account was incredibly influential. They write about having so little context for what was happening to them, because they had never known anything else.

That idea really stayed with me – the stripping away of identity, being reduced to a number, losing control over your body and self. It fed directly into how I approached Kali, especially visually and physically, with the shaved head and the institutional clothing. That loss of identity and agency felt essential to understanding who she is by the final season.

blue dress JENNIFER MILLEDER 

When you first read the finale script, what was your reaction to Kali’s role in it, especially knowing how long fans had waited to see her return?

I read it during the table read with the rest of the cast, and it was one of the most emotional days of the entire shoot. It was incredibly powerful, and I think that moment is going to be shown in the documentary. Every time I read Kali’s final scene, I just started crying – it was overwhelming.

I already knew Kali’s trajectory because Matt and Ross had told me she was going to die, but the rest of the cast and the crew didn’t know how their characters’ stories would end until that day. So being in the room and watching everyone react in real time to those endings was really intense and very emotional.

Kali’s presence in the finale is really pivotal. How conscious were you of playing something that could be interpreted in multiple ways?

I think that’s really powerful. I love that Matt and Ross have left space for the fans to decide what it all means. The fact that only they and Millie truly know how it ended, and whether Eleven survived, is brilliant to me. I think that’s exactly how it should be.

At that point, the story doesn’t belong to us anymore. You leave it with the fans, and they get to take over and finish it in their own way. I was just incredibly grateful to be part of that, and as an actor – and rooting for Eight – I thought the way they handled it was really beautiful.

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Farhad Nauman Niloy asks: one of the biggest debates since the finale centres on Mike’s version of events. What do you think of his theory about what really happened?

As I’ve said, only Matt, Ross, and Millie know what really happened. But I do have my own interpretation, and I believe in it because I believe Kali can change. For me, as an actor playing her, it’s about believing that she had the capacity to change, and that what Mike describes could have happened.

I don’t think Kali used her powers through anger this time. I think, if anything, it came purely from love for Eleven. That feels important to me. I’ve seen and read about people doing extraordinary things in the final moments of their lives, and I think that possibility exists here too. So yes, I believe it’s possible – that’s my interpretation.

The internet went into meltdown over what became known as Conformity Gate, with fans convinced a secret extra episode was going to drop. What was it like watching that unfold?

I honestly didn’t really know about it at the time. I only heard about it yesterday, and I was a bit like, ‘Oh my God, what is this?’ But that’s kind of the beauty of the show, isn’t it? The fan base is so deeply engaged, and people are willing to go that far with theories and ideas.

I think it’s incredible. I didn’t film an extra episode, but I did film the documentary, so I can confirm that much. But genuinely, how lucky are we to be part of something that inspires that level of passion and imagination? Kudos to Matt and Ross for creating a world that makes people want to dig that deep and keep the story alive themselves.

When audiences look back on Kali’s journey across the series, what do you hope they ultimately understand about her?

That’s a really, really good question. I think it’s about understanding how people can evolve, and about the purity of her intentions. You might not agree with the means she chooses, but her intentions are incredibly pure.

At the heart of everything, she deeply cares for Eleven. It’s always been about her, and about that relationship. Kali is trying to protect her in the only way she knows how. She’s terrified that Eleven will be taken back to the lab, tortured, experimented on, and ultimately killed – because that’s what she’s lived through herself.

When she talks about the choice they face, it isn’t about sacrifice in the abstract. It’s about preventing a fate she knows too well. In her mind, there are no good options, only unbearable ones. She’s trying to save Eleven from suffering, and she’s trying to save the other children too. Her thinking is driven by love, fear, and lived experience, not cruelty.

I hope people understand that Kali is acting from a place of protection and care. Everything she does comes from wanting to keep Eleven safe, even when the cost is devastating.

Stranger Things Season 5 is streaming now on Netflix.

Follow Linnea via @linneaberthelsen

Words Nick Barr

Photographer Jemima Marriott

Stylist Sayuri Bloom

Hair Emma Small

Make Up Charlotte Yeomans

Cover credits

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