Natalie Dormer has played the Queen of Westeros, the notorious Anne Boleyn, and the delightfully diabolical Jamie Moriarty. She’s played Cressida in Mockingjay, and Pvt. Lorraine in Captain America: The First Avenger. But for all the many complex characters Dormer has embodied, nothing compares to the challenge and vulnerability of her most recent role — and it has more impressed with her than ever.

In psychological thriller The Forest, Dormer portrays Sara and Jess: Twin sisters drawn into the thick of Japan’s Aokigahara Forest, a place where many go to contemplate suicide. After learning that Jess has disappeared, Sara gets a terrible gut feeling and flies to Japan to search for her. Once she makes her way to the forest, however, she’s warned time and time again not to enter, since it’s filled with thelingering spirits of those who’ve taken their lives — yurei who prey on the conflicted and the sorrowful.

Always the more confident and level-headed twin, Sara is determined to bring back her sister — so she enlists the help of an expat journalist named Aiden, and Michi, a forest guide. But once she enters Aokigahara, she finds it harder and harder to tell what’s real and what’s not. She starts to wonder if Aiden is truly an ally, or if he had something to do with Jess’ disappearance. And the forest itself begins to have its way with her psyche.

Wanting to know more about Dormer’s process and how she decided to take on this role, HG sat down with the immensely talented actress to ask a few questions.

HelloGiggles: Hi Natalie! So, let’s jump right in. What drew you to The Forest and your character(s) Sara and Jess?

Natalie Dormer: For me, it was the premise that I liked so much. I liked the original concept of a movie based around a relationship between two sisters, because you don’t get to see that very often. And the lead character is doing everything she’s doing out of love for her sister, and she wants to protect her. And also I was really intrigued by this premise that the forest is somewhere that reflects your own demons back at you. Because we all carry our own baggage and I was kind of impressed by this idea of what would happen if all our deepest fears we’re running from could manifest themselves physically. Because Sara is really in denial about something in her past.

HG: Yeah, exactly. There wasn’t much blood or gore. Much of the “horror” is all inside Sara’s head. Which is more shocking than anything physical, something I really loved about the movie.

ND: Yeah, I totally agree with you. It’s more scary what we do to ourselves and what’s inside our own head. One of the characters says to Sara, about the yurei, she says, “You do it to yourself.” It’s being out of control that is truly terrifying.

HG: Sara and Jess are similar, but… very different. Sara is confident, the one who takes care of things and people. Whereas Jess is portrayed as unstable and impulsive. How did you prepare to embody Sara and Jess? What was one thing that set them apart?

ND: Textbook, they look like opposite ends of the spectrum. You know, the controlled one, stable one, the alpha go-getter and then the wild child, the one who’s gone off the rails. There was so much in the writing already, that it was quite easy to get into character. The thing I loved about the script is the sophistication of it, it makes you think about a lot of things after you’ve seen it.

To me, it’s not necessarily apparent which sister is stronger. The one who seems more put together is the one who’s been running from something her whole life and has not faced the emotional truth. Whereas the one who’s always getting into trouble is brave enough to face the darkness in her life, and she’s in contact with her emotions. I liked that inverse symmetry.

HG: If Sara could pick one of the other characters you play to go with her into the Aokigahara forest, who would she choose? Because, after all, Aiden was probably a shaky choice.

ND: Well, having been in the field, so to speak, and somewhere else that is physically dangerous, Cressida is probably the best bet. Especially if she brings her semi-automatic weapons I was carrying in Mockingjay. Cressida is probably the most level-headed for that kind of physical, arduous experience.

HG: While The Forest forest part was actually filmed in Serbia, have you visited the real Aokigahara forest? What was it like? Did the film capture its true character?

ND: I did visit the real Aokigahara forest — as you can see from the beginning of the movie, we spent a week in Tokyo, and I managed to ride up to Mount Fuji and the true forest. The day I went was a beautiful day. The birds were singing, blue skies, families hiking along the path. I mean, it’s a place of outstanding beauty, you’re just aware. You see bits of rope disappear into the forest along your way. And “help” signs for people who are thinking of harming themselves.

And me, personally, I didn’t find anything eerie or spooky about the place. I just felt sad and compassionate and pensive, really, when you contemplate the people who go there to make that choice… This film has no intention whatsoever of being flippant about suicide. To the contrary, the whole point we’re making in the movie is that when someone who you love needs help, you do everything in your power to help them. The humanity of the place I found most affective.

Watch a clip of The Forest below:

*Interview has been edited and condensed

(Image via Gramercy Pictures)