Oliver Lang / AFP / Getty

In late 2012, news broke around the world that a nanny on the Upper West Side of Manhattan was accused of fatally stabbing two young children in her care. Paris Match deemed the perpetrator of this “inexplicable” act “la nounou de l’horreur”—the nanny of horror. As the children bled in the bathtub, reports said, the nanny—who was so close with her well-to-do employers that they had earlier that year spent several days visiting her relatives in the Dominican Republic—slashed her own throat. (She survived, and has pleaded not guilty to killing the children.) To most parents, the headlines were a chilling reminder of the vulnerability of children and the cruelty of which their adult caregivers are capable. To the French-Moroccan writer Leïla Slimani, who had a toddler of her own, the tragedy was the perfect creative catalyst. She knew she wanted to write about a nanny; now she had her opening.

Slimani’s Goncourt Prize–winning 2016 novel, Chanson Douce—published this month in English as The Perfect Nanny—lands its biggest punch on the first page. “The baby is dead,” Slimani writes. “It took only a few seconds.” His sister, still alive when the ambulance arrives, has had her lungs punctured, “her head smashed violently against the blue chest of drawers.” Louise—the nanny, the killer—is not yet named, but her presence is noted. The paramedics “had to save the other one too, of course. With the same level of professionalism; without emotion. She didn’t know how to die. She only knew how to give death.” This is no mystery novel. The question at the heart of the book is neither who nor how but why.

If the premise of The Perfect Nanny is its violent denouement, its subject is far more ordinary. Set in Paris’s 10th arrondissement, it is, in many ways, a novel of manners, a deft portrait of bourgeois family life in the 21st century. (Slimani’s first novel, forthcoming in English as In the Garden of the Ogre, was inspired by the Dominique Strauss-Kahn affair.) Immediately following Slimani’s brief, grisly mise en scène, the book goes back in time. Myriam, “the most dedicated student” in her law school class, has stayed home since the birth of her children, Mila and Adam. Her husband, Paul, works in music production. The arrangement has suited the couple for a while—having a second child “was an excuse not to leave the sweetness of home”—but spending her days with two young children has made Myriam “gloomy,” and jealous of Paul’s career. When she gets an opportunity to go back to work, they agree to look for a nanny.

Myriam and Paul, wary of entrusting their children to a stranger for the first time, want their prospective caregivers to prove that they are responsible. As important, they’re hoping for the chance to prove something themselves: to show “that they are good people; serious, orderly people who try to give their children the best of everything.” The choice of a nanny, Slimani shows, has as much to do with how adults see themselves, with how they would like to be seen by others, as it does with a family’s practical needs. When they meet Louise, the choice is “instantly obvious. Like love at first sight.” The children adore her. Her references are impeccable. The parents are “charmed” by Louise’s “smooth features, her open smile, her lips that do not tremble. She appears imperturbable.” She is, they soon decide, “a miracle-worker.”

Slimani, for her part, doesn’t seem to believe in miracles. She’s interested in the circumstances that lead parents to seek them—and in the ways that children respond to being cast as actors in adult fantasies. Her descriptions of Mila and Adam’s interactions with Louise are finely attuned and—given what’s coming—haunting in their intimacy. To know that each morning Adam “welcomes [Louise] with gurgles, his plump arms reaching out,” or that Mila is the kind of child who “doesn’t stop until she comes to the very end of the sidewalk,” is to know too much about these siblings whose awful fate is already sealed.

Except this, too, is part of Slimani’s project: The children who are dead at the beginning of the book are shown throughout not as idealized innocents, but as complex beings who navigate adult whims, and the line between danger and safety, with a clarity that eludes their elders. They are well aware that their needs shape the lives of the adults around them, and they wield this power deliberately. Mila, Slimani writes, “watches herself in the mirror when she cries.” After running too far ahead of Louise, “she makes it up to the nanny, clinging to her legs.”

Louise’s bond with the children—and with their parents—has a dark underbelly, of course. Her attentiveness goes hand in hand with her obsessive tendencies; her willingness to give her all to the family masks her desperation to escape a difficult past. Yet Slimani has distributed neurosis generously among her characters: Myriam and Paul, too, seem acutely on edge. Their “cocooned existence” as young parents kept them “far from the world and other people, protected them from everything,” they once believed. That illusion was quickly shattered as Myriam began to feel that the children were “eating [her] alive.” In Slimani’s telling, it was not Louise who penetrated the security of the cocoon—that inevitable rupture happened of its own accord.

Slimani is preoccupied by the paradoxes of parenting in a world where the potential for disaster abounds. When it comes to the safety of their children, Myriam and Paul are at once irrationally scared and naively—tragically—self-assured, invested in their own power to maintain control. Watching Louise play with Mila and Adam, Myraim “feels troubled” and “horribly embarrassed” as the nanny writhes and shrieks in character. Louise, Myriam thinks, looks drunk. But when she laughs, it’s “a laugh that still belongs to the imaginary world in which their game is taking place,” and Myriam tells herself that perhaps “Louise is simply a child too.” The scene is an obvious foreshadowing of violence to come, yet to see it merely as that is to miss its depth.

Being the perfect parent is ultimately an impossible task, Slimani reminds readers, not least because the horrors of adult actions can never be permanently kept at bay. In the park, women are “suspicious of men who come near,” she writes. “They drive away the men who smile at the children, who stare at their plump cheeks and their little legs.” She refers to Paris’s terror attacks only obliquely, but notes that since the attacks, Myriam has forbidden Louise to let the children watch television, as if such a simple ban could maintain the sanctity of the cocoon.

Even as her taut prose highlights the absurdity of such illusions, Slimani’s empathy for the parental love and care that necessitate them is clear. She is not out to blame the parents for the fate of their children. If anything, Slimani portrays Paul and Myriam as unreasonably protective. Returning home one day, Paul finds that Louise has painted Mila’s nails and put makeup on her. Louise and Mila are laughing, but Paul feels as though “he has walked in on something sordid or abnormal.” In his fury, “he grabs Mila by the arms” and starts removing the makeup.

“You’re hurting me,” she sobs. “He has the impression that he is disfiguring her even more, soiling her, and his rage grows.” The danger, here, is inane, and in attempting to take charge, Paul winds up causing further damage. The point is not what the nanny has done. Instead, the fact of her having done it has reinforced a truth Paul would rather not confront: Children grow up and become soiled.

In the end, Louise’s particular twisted motives don’t really reveal anything essential about the pitfalls of modern child-rearing. Though portions of the novel are told from Louise’s perspective, and though Slimani fills in enough of the nanny’s dysfunctional history to make her obscene final act feel plausible, she remains something of an enigma—deliberately so. Readers aren’t likely to converge on a single interpretation of why Louise has done what she’s done. Ultimately, she holds sway as a symbol rather than as a psychological reality, a choice that makes this deftly told tale all the more eerie. Parental ideals of perfect safety and fears of imminent calamity are embodied in Slimani’s nanny, who invites—and flouts—the faith that anyone can assure one and prevent the other. That her power to do both is so ordinary only makes it more horrifying.

We want to hear what you think about this article. Submit a letter to the editor or write to letters@theatlantic.com.