In the summer of 1997, when I was eleven, I had an abnormal appetite for books. I wasn’t particularly picky about what I read. Every week, I went to the local library and scanned the middle-grade and young-adult shelves, zeroing in on spines that caught my attention. I then examined the covers and jacket copy of those books with the solemnity of a scholar. If a book passed muster—and it usually did—I put it in my special red library tote bag, which my parents bought for me with the explicit purpose of limiting the number of books I brought home.

That was the summer when—tan, smelling of chlorine, stippled in mosquito bites and goose bumps from the air-conditioning, just on the verge of puberty—I discovered Lois Duncan. Her books’ dramatic titles, such as “Summer of Fear,” “Killing Mr. Griffin,” “Gallows Hill,” drew me in, and their taglines sealed the deal. I wedged as many as could fit into my bag. Horror novels had been banned in my family since I was seven, when an older kid on the bus let me borrow his copy of “Night of the Living Dummy,” and it gave me such terrible nightmares that I insisted on sleeping with the lights on for a week. So, when my mother picked me up from the library, I pleaded my case. Most of them had been written in the nineteen-seventies, I told her. (I had checked.) How scary could they be?

Very, of course. The climax of “Gallows Hill”—in which a girl’s classmates believe her to be a witch and gather on a hilltop to hang her—was so thrilling that I literally trembled. (Only when it was over did I notice that, while I was reading, I’d moved to the arm of the couch and perched myself there.) I picked up “Summer of Fear” next: a teenager’s beautiful cousin moves in with her family after a terrible tragedy and begins to steal the protagonist’s life. After that, “Killing Mr. Griffin,” about a group of high-school students who accidentally kill their English teacher. Then “Daughters of Eve,” in which a teacher runs a feminist organization to instruct her students about the poison of regressive gender roles—but her message of empowerment is tinged with something sinister.

These novels weren’t scary in a way that I recognized. They walked a delicate line between impossibly terrifying and terrifyingly possible. Duncan has sometimes been grouped with writers like Christopher Pike or R. L. Stine, but her novels lack the comic, pulpy luridness of their work. Her prose is unfussy and clean. She centered her books on young women, and her writing considers themes that have come to obsess me as an adult: gendered violence, psychological manipulation, the vulnerability of outsiders. She writes about folie à deux and mass hysteria, doppelgängers, sociopathy, revenge. She portrays psychic powers and past-life regressions with a kind of realism; she recognized that even a supernatural evil must have a human heart.

I brought the finished books back to the library a few days later, and found more titles that had recently been returned. And so her books came to fill that summer, when everything from thunderstorms to my mutating body began to inhabit a space in my mind somewhere between menace and excitement. Near Halloween, the film adaptation of one of her best-known novels, “I Know What You Did Last Summer,” came to theatres. My parents wouldn’t let me watch anything R-rated, so I didn’t see it until years later, at a sleepover. In the standard, self-righteous fashion of a bookworm, I thought the movie was terrible.

The following summer, I learned that the library had a book by Lois Duncan that I had missed, because it was shelved in the nonfiction section: “Who Killed My Daughter?”

On a rainy July night in 1989, an unknown assailant drove up next to the car of Duncan’s youngest daughter, Kait Arquette, and shot her in the head. “Who Killed My Daughter?” tracks the family’s attempt to solve the case, which the police concluded was a random drive-by. It is written with Duncan’s usual knack for vivid detail, but her raw grief is nonetheless on full display; in one heartbreaking scene, she fantasizes about tying her daughter up with rope on that final evening, thus preventing her death. Reading it made me feel like an interloper, invading someone’s private pain. The book was my first exposure to the genre of true crime, and it was devastating.

Particularly alarming to my young self was Duncan’s profound belief that she had somehow predicted many elements of her daughter’s murder in her novel “Don’t Look Behind You,” which was completed just before Kait was killed. The protagonist of the novel is modelled after Kait, and the book was dedicated to her. One of the suspects in Kait’s murder had the same name as the book’s hit man. After Kait’s death, a medium worked with a sketch artist to create a picture of her killer, and the resulting drawing matched the drawing of the hit man on the cover of the British edition of “Don’t Look Behind You.”

“Who Killed My Daughter?” tracks Duncan’s trajectory from psychic-skeptic to full-blown believer. When I finished the book, with no answers, I didn’t know what to do with myself. I was twelve. I understood the concept of nonfiction, but I didn’t understand how a discussion of psychics and premonitions—phenomena I was pretty sure I didn’t believe in—fit into it. And yet Duncan believed in them so strongly, and she described events that seemed too strange to be coincidences. I felt shredded by the lack of resolution, and by the gulf between all of her novels and this real-life horror.

“Gallows Hill” was published the summer I’d first discovered Lois Duncan; much later, I learned that she had managed to complete it only after years of difficulty. She never wrote another thriller, supernatural or otherwise. In 2014, she told a writer for BuzzFeed why. “I went weak after Kait’s murder,” she said. “How could I even think about creating a novel with a young woman in a life-threatening situation?”

Three years ago, Duncan published an e-book sequel to “Who Killed My Daughter?” called “One to the Wolves.” I tried to read it, but it hurt as badly as its predecessor had, and I stopped. The theories around her daughter’s death have taken on that troubling sheen of conspiracy: either the murder was part of an elaborate coverup, or Duncan’s search for her killer was a grieving attempt to impose order over chaos, meaning over meaninglessness. It distresses me that I cannot tell the difference.

But I have found myself, in many ways, returning to her other books. As I found my own voice as a writer, I saw that my work was tangled up in Duncan’s influence. I went through a phase in which I was constantly burning down buildings occupied by my characters—and realized one day that these set pieces were all indebted to the fire at the climax of “Down a Dark Hall.” I can’t escape that eerie, liminal space she explored, between ordinary reality and the unexplainable. And the memory of Duncan’s girls—how important it was to me, at the age of eleven, that they were the heart of their own stories—echoes through my fiction. All of my protagonists are female, because they need to be.