If you were an adolescent girl of a certain age—born somewhere between 1972 and 1992, caught between Gen X and millennial—you read Lois Duncan. If you didn’t read Lois Duncan, your friends did, and if they didn’t, their friends did. Duncan wrote nearly fifty novels, with titles like Summer of Fear, Stranger With My Face, and Killing Mr. Griffin; on each paperback cover, a portrait of a teenage girl with wide eyes and brown hair, haunted by something just out of sight. Fear, in Duncan’s world, lurked in a school hallway, in the eyes of a friend, in the trust of a teacher. Her novels revealed the small betrayals of teenage life, magnified in blood.

Lois Duncan—the pen name of Lois Arquette, who died on June 15 at age 82—had a canny brilliance all writers strive for: To create work that was intense and personal that also spoke to millions. Ask a Duncan fan, and there are legion, and none will have the same answer for their favorite novel. All, I may conjecture, will have the same underlying reason: they gravitated to what they feared most.

Books for teens had previously been sweet, even saccharine, like Maureen Daly’s story of two good-hearted Wisconsin teenagers in love, Seventeeth Summer (1942); socially conscious, like Paul Zindel’s The Pigman (1968) in which two students befriend a middle-aged outcast; funny and all-too-real, like most of Judy Blume or Louise Fitzhugh; or on-message, like Beatrice Sparks’s “anonymous” 1971 drug diary, Go Ask Alice.

These books understood that girls of a certain age grapple with changing bodies, hidden longings, raging desires, and quaking needs. Duncan went even further, understanding that young girls also feared what those emotions could do, both to themselves and to those around them. Mysterious forces act on the heroines of Duncan’s books, as their developing adolescent personalities become the ideal vessels for ghosts, specters, and otherworldly phenomena. Kit, the heroine Duncan’s Down a Dark Hall (1974), is isolated in a spooky, Gothic boarding school by phantoms real and imagined, compelled beyond control to act as amanuensis for dead authors such as Emily Brontë.

Duncan knew about the young girl’s primal fear about belonging to the wrong group, or being excluded from the right one, and she infused both premises with terrible consequences, from the cult-like enclave of young women in Daughters of Eve (1979), the perversion of authority in Killing Mr. Griffin (1978) and the nasty secret binding friends with lethal toxicity in I Know What You Did Last Summer (1973).

“Life continues, and we all of us keep changing and building, toward what we cannot know,” Duncan wrote in 1981’s Stranger with My Face. Doubles recur in her best work, especially those who seek to obliterate the heroine. Summer of Fear (1976) reads now like a chilling portrait of borderline personality disorder, as Rachel realizes before anyone else that her visiting cousin, Julia, is a vicious snake hiding behind a charming exterior. Laurie, the accomplished protagonist of Stranger With My Face, does near-literal battle with a version of herself. In Duncan’s world, teenagers, above all, feared themselves, and capabilities previously unknown to them.

Duncan’s understanding of how teenagers think and feel was largely instinctual, but all she had to do was take a look around. Adolescents had more buying power and greater autonomy, yet their wants and needs remained a mystery to the media. Witness the Newsweek 1966 cover story which interviewed hundreds of teenagers and returned with a lighthearted conclusion: “A solid majority a builders not breakers…they want what the adults want them to want. They are essentially content with their lot.” The biggest problem, according the survey, was the pressure to cheat to get into college. But the sexual freedom of Haight Ashbury gave way to the calamitous horror of the Manson Murders just three years later. Girls hitchhiked in a bid for freedom away from restrictive parents still in thrill to the gray flannel suits, only to find themselves prey for freeway-haunting serial killers.

Duncan found her niche by an accident of the market. A veteran of magazine publishing—her first stories appeared at the age of 13 in Redbook, Reader’s Digest, and Good Housekeeping. In 1966 she happened to publish two very different books with the same publisher, Doubleday, which would decide the path of her career. Point of Violence is typical a suspense novel for adults: A young, widowed mother hides out on secluded beach to grieve while a stalker, who may be her husband’s killer, taunts her with psychological games The book emulated the best work of domestic suspense masters of the day, such as Charlotte Armstrong, Margaret Millar, and Dolores Hitchens. Ransom, is a nerve-quickening account of high school kids held hostage on their school bus by a deranged man who has killed the driver. The fast pace spares no time for sentimentality and the ending, while satisfying, is not without bloodshed.

Ransom pointed towards a new genre of popular fiction: the young adult novel. Books geared specifically toward teenagers were not yet in vogue, existing as a nebulous state between children’s and adult literature. Madeleine L’Engle’s A Wrinkle in Time, S.E. Hinton’s The Outsiders, the early works of Norma Klein, even Harper Lee’s To Kill A Mockingbird, so widely taught in high schools since its 1960 publication can be characterized as YA today, but teenagers did not have this distinct category in the publishing marketplace.

Half a century later I still think of Ransom with a sense of dread. Part of it is retroactive—the novel was published the same year of Charles Whitman’s mass shooting at the University of Texas-Austin—and another part is how it was predictive, eerily similar to a 1976 school bus kidnapping of children in Chowchilla, California. Duncan wold perfect that creeping sense of paranoia during her decade-long peak from I Know What You Did Last Summer to The Third Eye, coinciding well with the dread suffusing the country in the post-Vietnam, post-Nixon America.

Duncan herself shied away from putting her work in larger context—“The author-reader relationship is a two-way street. The receiver who interprets the story is as important as the person who created it,” she said in a 2011 interview—but the fractured, haunted, and terrorized lives of Duncan’s teens are symbiotically connected to the issues urgent for young people 1960s and early 1970s America.

Duncan’s way with fear would have cruel twist: Her youngest daughter, Kaitlin Arquette, was murdered in Albuquerque, New Mexico in 1989. The murder remains officially unsolved, and Duncan spent the rest of her life trying to find her daughter’s killer. Her publishing pace slackened as Duncan’s priorities shifted to chronicling the uncertainty and bitter frustration of an unresolved crime so close to home.

Her 1992 account of Kaitlin’s life, death and the botched investigation, Who Killed My Daughter? is by necessity a difficult read. “I have lived that evening over so often in my dreams that by now it has become an extension of myself,” she wrote. The lack of justice for Duncan is a stark reminder that real life doesn’t guarantee an ending as does a novel. It is a reminder that the safe, stable, placid life is an illusion. Teenage girls always knew this. Because Duncan did, too, that’s why the bond between her and her readers feels like sacred kinship.