In Rory Power’s latest YA psychological thriller Kill Creatures, her first non-speculative novel, a missing teen resurfaces, to the immense surprise of her murderer. A year after Nan secretly killed her best friends Edie, Jane, and Luce during a moonlit hike into Saltcedar Canyon, Luce is found floating in the lake, alive but with no recollection of what happened or where she’s been. Now a panicked Nan struggles to appear supportive of Luce and the newly reopened investigation even as she scrambles to obscure the facts—or at least the facts as Nan remembers them. Power spoke with PW about exercising new writing muscles, unlikable female characters, and the allure of the whodunit genre.

Readers know who the murderer is at the beginning of Kill Creatures. What inspired this angle?

I love whodunits; I get such satisfaction out of those books. But I think that kind of story structure is also inherently a whydunit because they never stop at just finding out who the killer is. Readers want to know the whole story. I thought of writing Kill Creatures as a challenge for myself as a writer. What if I answer the first half of the “who did it and why” immediately? What do I then have to do to make sure the story still has an arc and still has engagement and intrigue for a reader?

Did you worry that readers would find it difficult to empathize with Nan?

When I sit down to work, likability and relatability aren’t necessarily at the top of my list of things that interest me. The main characters of my previous books are not the most likable people. I don’t think Kill Creatures requires that you like Nan. My hope is that readers engage with her story. Maybe for some of them it’s about wanting to see her get her comeuppance. Maybe others relate to her friendships. Just as the structure of the book was a challenge to me as a writer, I think writing a character like Nan was also a challenge. How do I build this person so that even if you hate her, you want to turn the page?

Chapters alternate between before and after the girls’ disappearance. How did these timeline shifts inform Nan’s narration?

I feel like the Then and Now construction is such a classic of the thriller genre. Whenever I see a book that has that, I’m locked-in, so it felt like a natural thing to include. In terms of Nan specifically, I think so much of her arc is about memory and perspective. Creating these two timelines where Nan Then and Nan Now are almost different characters who operate on such different bases of knowledge helped play into the overall thematic idea that Nan is a person who—as we all do—contains multitudes. Hers are just a darker shade.

The defining difference between the two that I tried to keep in mind was that Nan Then is much more earnest, whereas Nan Now has an edge of nihilism to her. She thinks, “Well, the worst has already happened, so this might as well happen, too.” She thinks, “I did it, so I don’t have anything to be afraid of anymore. I don’t have anything to lose.”

How did the process of crafting Kill Creatures differ from your previous novels?

This book was different for me in a couple ways. I keep a running list of places that I think are interesting, or Wikipedia articles about places that I want to keep reading about, and I just had “canyon” on my list. I didn’t know what that meant exactly, but that was the starting point—an interesting place, an interesting vibe.

In my notes to myself, I call Kill Creatures my reverse Pretty Little Liars book. I just had this image of a girl leaving letters to her friends at the edge of a canyon, and one day she finds that there’s a letter written back. But when I couldn’t take that any further—why are they writing letters if they had phones? I ended up taking it to an extreme, where it’s a literal person who comes back instead.

But it wasn’t until I had Nan that I could really figure out what kind of setting would make sense for her. Having a specific character and a specific hook was new for me.

What were some things that challenged or excited you about writing your first non-speculative novel?

Writing it was easier than I thought it would be. I thought that the impulse to include speculative elements would be hard to control, but it turned out that there were a lot of other places I could put the weird. It could be speculative, but what if instead of including it externally, I just put all that into the character, and what if the off-kilter imagery that I wanted to use could play on reality? What if those elements are just in Nan’s head because that’s how she thinks? How can I take what I know how to do and make it a challenge? It was a really exciting way to exercise new muscles as a writer.

What other media influenced Kill Creatures?

There were a lot of things in the mix. I’m inspired by a lot of visual artists. My mom used to talk about the Peter Weir movie Picnic at Hanging Rock when I was growing up. As soon as I was old enough, she sat me down and made me watch it. That imagery of girls disappearing into the landscape was very front of mind.

Gone Girl was also implanted in my brain. I always thought of it as Nan thinks that she’s Amy Dunn, but she’s actually Nick, and the real Amy of the narrative has been there the whole time, waiting for their chance.

Then there’s a couple moments in Pretty Little Liars where the show sets up that one of the main characters maybe killed someone. But after a couple episodes, it’ll be like, “No, don’t worry, they didn’t do it,” and I just kept thinking, “Let them kill people!” That would be so interesting. It would even make sense for some of the characters. It just seemed like, maybe not a missed opportunity, but an opportunity, nonetheless.

How did you arrive at the twist ending?

I always knew that there was going to be a character who would act as the other side of the coin for Nan. But as I was writing, I wasn’t sure how far I wanted that to go. I’m not an outliner. Most of what keeps me engaged when I’m writing is the discovery part of it. When I got to the last chapter, I decided I wanted the book to have that classic horror movie ending where you think the monster’s dead and then, right before the credits, it opens its eyes and you’re like, “Oh no.” I couldn’t do that with Nan, because her story wraps up exactly in the way I wanted, but that other character could be the monster. It made a lot of sense for them.

Nan’s whole story is about how she does this really bad thing, and now there’s a part of her that thinks of herself as a human who does bad things. But then, as she goes through her story, this other character makes her realize, “Well, Nan, you’re not the only one who’s capable of that.”

Kill Creatures by Rory Power. Delacorte, $19.99 June 3 ISBN 978-0-593-30231-6