From creator Antonio Campos and inspired by a true story, the HBO Max original limited series The Staircase tells the story of Michael Peterson (Colin Firth), who was accused of killing his wife Kathleen (Toni Collette) after she was found dead at the bottom of their staircase. The suspicious circumstances, along with secrets that start to unravel, create a stranger-than-fiction vibe that make you wonder just how accidental this tragedy truly is.

During this interview with Collider, co-stars Firth and Collette talked about why they connected with this story, that the series has a more balanced perspective between both Michael and Kathleen, deciding not to make any definitive judgments on Michael Peterson, the strange experience of shooting this death scene, and what they hope people take from watching this.

Collider: What was it about this story that you found yourself connecting to? Was there something specific about either the story or the characters that’s what ultimately got you to do this?

TONI COLLETTE: I think it’s the unknowable aspect of things. The story is entirely compelling because it’s just this domestic world that goes horribly wrong. These people have incredibly beautiful bonds. It’s actually the story of a breakdown of a marriage, and then all of it happens beyond that. Unlike the documentary, you get to know Kathleen a bit more. The perspective is a bit more balanced.

COLIN FIRTH: I don’t know if it was initially the content. I just sensed good writing. I could sense there was something very, very alive and authentic, coming off the page, within the first few pages. There was something about the pace. There was something that intrigued me. I didn’t know anything about Michael Peterson or The Staircase, so I came to it fresh, and I just saw something happening as I was reading. That’s not an everyday experience when you read scripts. So, it was that, and then feeling like I wanted to understand.

There was something that was slightly beyond my grasp, but it felt very real. There’s nothing like a mystery. You keep chasing it down. And then, there was a documentary and I started watching that and thought, “I already know this guy, or these people, from just having read two episodes.” That’s a testament to how rich the writing was. It just led to one question after the other, and I never got to the end of it, really. It was the pursuit of that, that drew me in.

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Image via HBO Max

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Colin, how did you view Michael Peterson? He’s a guy who’s presenting this idea of himself, and he clearly has secrets and aspects of his life that he’s not sharing with people, so how did you humanize him? What was it that really helped you, in that sense?

FIRTH: I actually don’t quite know how to answer the question. I kept trying to find a way through. I was connecting parts and things that I could explain. I could get somewhere with that, but I would join three dots and couldn’t find the fourth. So, in the end, instead of looking for something that I could settle on, as a returning point, a base, or a core, and saying, “Whether I reveal it or not, I can make this decision about this character,” it somehow wouldn’t let me do that. In some ways, I gave into that being the experience of acting him. It was a very unusual one.

Having not really made any absolutely definitive, final decisions and judgments on this character, it made me wonder whether that is something I should have done with every character. Maybe it’s a facade to make a decision about your character. Maybe nobody is that simple. I think there is something quite particular about Michael Peterson, in terms of the question you’ve just asked, but to some extent, we are probably all performing some version of ourselves. We make choices in how we dress. We have social graces that we observe, and we’ve learned. Nobody is an open book. One uses the little bits and pieces of those universal truths and just amplifies them, in the playing of this character.

Toni, I don’t think it’s a spoiler to say that your character dies, and we see how your character dies.

COLLETTE: Not at this point, no.

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Image via HBO Max

What was it like to shoot that and to spend what I would imagine was a decent amount of time shooting that? What were the biggest challenges for you, in doing those moments?

COLLETTE: Look, it’s strange. I have found it strange in the past, dying on screen once within a story, so having to do it three times was strange. It was strange. There was a certain controlled element about it that was very specifically choreographed, in terms of the knowledge we have about where Kathleen’s head hit certain parts of the staircase and what needed to be seen, how she may have been, and how she moved, just so that I matched the markings on the wall. There was that element of it, but then there’s just the responsibility of bringing some truth to it. I’ve clearly never died, and I’ve never seen anything like that. There’s so much we don’t know about how she died. So, having the opportunity to do it three different ways was really interesting.

It was a bit of pressure. We did a certain amount of rehearsing, but then once those blood tubes were attached and were in that wig, I really only had one take. I had to move beyond the fear of that and just, no matter what time of day we shot it – sometimes it was two in the afternoon, and sometimes it was five in the morning – it was just a matter of recognizing the shape of what I had to do and honoring that. You just have to give over to something and hope that it appears real. Otherwise, you’re wasting everybody’s time and everyone’s tired.

Also, a person died and there is such a responsibility that goes along with that. I just wanted to bring something real and bring something that honored her life. On the page, Kathleen seemed pretty clear. In a way, I had a certain amount of freedom because everybody else is still alive, and I didn’t really have much more to go on, other than what they say about her in the documentary. My Bible were the scripts and the words. Up until that point, she has moments of huge stress and exhaustion, but she actually loves her life and she loves the people in her life. Getting to know her just makes it all the more tragic.

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Image via HBO Max

It’s so easy to get caught up in these types of stories and these true crime dramas, and forget that there are real people involved. What do you hope and what would you want people to know about these two individuals?

FIRTH: What I really hope is that, if one does contemplate this story, it is from the vantage point of Kathleen being alive. In some ways, she’s the most clearly vivid presence in this story. In the documentary, we see family photos and autopsy pictures, and we hear her described every so often, but it’s not just the subject of a puzzle, it’s the person. The full devastating tragedy of this has to be appreciated in the light of a very, very vital and vivid human being, otherwise, it’s just a genre exercise. Often, victims and perhaps female victims are just reduced to autopsy pictures, even to the point of being fetishized, in terms of something that is consistent with a genre. The two things that grip me the most, that are at the very center of this, are Kathleen and her humanity.

The other is the fact that there’s a paradox in the documentary because it's seemingly recording something that’s just happening, as a fly on the wall thing, and it’s not really making itself self-evident with its own presence. It’s a film. It’s saying, “These are just people having breakfast and this is just something that’s happening,” but there’s a bloody camera in the room and a microphone, and people, and the people that you’re watching all know they’re being watched. To pull back that lens and say, “Yeah, they are having breakfast, but they’re having breakfast while being watched,” so we’re watching that as they’re watching them. It’s making that explicit, in a way that the naturalism of a documentary, by nature of its form, is pretending isn’t there.

The Staircase is available to stream at HBO Max.