Ross Lynch may currently be known as the nonmagical dreamboat in Chilling Adventures Of Sabrina, but his most recent foray into film was far more sinister. In My Friend Dahmer, Lynch plays the titular serial killer when Jeffrey Dahmer is still in high school—a few years before his first murder. The original work was a graphic novel of the same name, written by John “Derf” Backderf, a childhood friend of Dahmer.

The film chronicles Dahmer’s troubled teenage years, his mother’s descent into mental illness and fraught relationships at school. Despite being an outcast, Derf and his friends add Dahmer to their group—even going so far to create the tongue-in-cheek “Dahmer Fan Club.”

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So it was certainly a challenge for Lynch. However, he wasn’t initially fazed. “My process toward acting changed a bunch,” he says of his years between his Disney projects and Dahmer, “but it’s always evolving, and I’m always changing it, no matter what I’m doing.” Lynch’s work had previously been primarily comedy-focused, so what was it like to handle such a dramatic tone switch? “Surprisingly, I found a lot of similarities in the [acting] process,” he says. “It’s a lot darker and serious concept matter. It was kind of a familiar experience, even though it was such a different story to tell.”

Of course, he did have to work a lot harder to “leave behind” his work on set—something that wasn’t as terrifying when he was trading riffs on Austin & Ally.

“You’re still existing between action and cut,” he says of his process in removing himself from the terror of Dahmer’s actions. “[But] whenever you expose your mind to anything, your subconscious is listening. Inevitably, I did have strange experiences, because of what I was living at the time.”

One of My Friend Dahmer’s most chilling choices was filming in Dahmer’s childhood home. “That was the strangest part of doing Dahmer,” Lynch says. “Filming in his childhood house where he took his first victim’s life...there were definitely some...energies roaming around.”

Not only did the shoot have special location privileges, but also the writer, and childhood friend, Derf, would sometimes be on set. And, according to Lynch, this led to some unsettling conversations.

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“At one point,” Lynch says, “Derf was sitting across from me—I think we were in Dahmer's house—and I had the whole getup on, the glasses and everything, and we were in the middle of a conversation, and suddenly he was like, ‘Dude, I’m sorry. You gotta take the glasses off or something. I don’t wanna look at you. You’re reminding me. You look exactly like him, and I’m kinda freaking out.’ ...That was a pretty surreal experience.”

You can read more about Lynch and his acting travails in the Driver Era cover story, which is available for preorder here.