ENTERTAINMENT WEEKLY: How much of the story were you allowed to know before shooting?

MADISON ISEMAN: None of us knew anything. You’re really watching our characters trying to put this whole thing together just as much as we are. Is it my favorite way to work? Ideally, no. I very much like to know, so I can make my character arc from the very beginning, but this is a different way of working. I’m not kidding, we were all so stumped on set.

The show does such a good job of setting up so many different opportunities for people to step into that world of possibly being the killer. It’s a hard show to read, but I will say, if you really sat down and tried to put all the pieces together, you could figure it out. All the information is in front of you. The payoff is really rewarding.

Let’s get into your various roles on the show. Not only are you playing twins, but with the twin switch in the pilot, was it like you were playing almost three different characters?

Yes, very much three different characters, and it was complicated. It took a lot of preparation and trying to figure out who these girls were apart from each other, but also who they were together, because you really see them together for the majority of the pilot episode. And they’re completely different personalities, but at the same time, they share a similar darkness and this experience from their mother committing suicide when they were younger. Where Lennon very much keeps that darkness tucked away, deep down inside of her, and puts on a facade when she walks in the room, Allison very much puts it on display for everyone to see.

What went into playing these roles technically?

I definitely wasn’t sure what the technical side was going to be like, and if you think about it, it’s double everything. It’s double the time, double the memorization, but we had a really great team working with us. My acting double is fantastic and made it easy, but it was long, emotional days with the twins. But then you have the switch with the third character, I guess you could say, and I feel like that was more just a game of tug of war, of how much Allison is able to shine through Lennon.

The audience is given the treat of being able to watch the show from the perspective of knowing something all the other characters don’t, which sets up the story for an interesting viewing experience. I was able to play a bit more with the fact that I can let Allison through a little more at times, and it’s okay if the audience can see that.

Did you do anything to help switch your mindset when you had to change characters? Did you have to listen to a different playlist?

I always thought of them as different pairs of shoes. When I would put on my Lennon boots, it was a full physical body change. It was the way she walks in the room and just stands up straight. She’s the kind of girl who reaches out to people. Allison is much more reserved and doesn’t like to be touched — she’s insecure with her body. I definitely used a lot of music. I think I had my headphones in pretty much the whole time. I journaled for both of them, so every time we would do a switch, I would usually try to go back through and read a couple of entries I made from the perspective of one of the different characters, just to get in that head space.

I do want to talk specifically about the scene where you’re in the water with your sister’s dead body in episode 4. How did you film that?

We tried it many different ways. We weren’t sure if we were going to do face replacement or if we were going to do a full split-screen replacement. I think in the water, what they ended up going with was a full face replacement. I think the other body you actually see is my acting double. And I don’t know if you’ve ever floated in the water for that long, but it was hard playing dead floating in the water. I think we ended up taping water bottles full of air underneath my back, just to keep my back straight, because when you’re not moving, it’s borderline impossible to completely stay afloat the way they wanted me to. That was an interesting day, but it turned out really great.

I love that moment because you all had been building to the question of: Is it going to be the movie twist? Is she not dead? And then to have her body show up, it let the audience know you were doing something different.

Yeah. And I love that we play into that, because I think that’s what everyone will be expecting. People are pretty clever nowadays, and they’ve seen pretty much every twist you could possibly come up with. I think initially, that’s what everyone’s going to think. And so it’s such a fulfilling moment in episode 4 when that finally comes out — that she is dead.

Do you have a favorite episode?

Oh, yes, I do. It’s episode 8, and I literally can’t get into why. We very much give a bunch of different puzzle pieces, and you’re able to see the perspective of the grad night from many different places, and things change. And then it’s all so confusing, and by 8, it finally all makes sense. It was just the perfect way to wrap up the show.