At a bank in the border town of Nogales, a Mexican woman named Lydia attempts to withdraw cash from her dead mother’s account. She needs $11,000 to pay a smuggler to lead her and her 9-year-old son into the United States. But when the bank manager asks for documentation, Lydia can’t supply any. Less than two weeks earlier, her mother, her husband and the rest of her family were murdered at an afternoon barbecue. Lydia and her son, Luca, have since then been on the run.

Up to this point, two-thirds of the way through Jeanine Cummins’s thrilling and devastating “American Dirt,” I’d devoured the novel in a dry-eyed adrenaline rush. Lydia, Luca and the teenage Honduran sisters they’re traveling with — who are fleeing gang violence — leap on top of freight trains. They endure kidnapping, rape and the constant threat of death. “If there’s one good thing about terror,” Lydia thinks wryly, “it’s that it’s more immediate than grief.”

For a brief time, in the bank, Lydia allows the grief in. She looks at the manager and decides to tell her everything: “She will throw herself on the mercy of this stranger’s kind face.” In turn, the manager reveals that her nephew disappeared the previous year and was found with his head separated from his body. This encounter, the confession of private horrors within the formality of an office cubicle, affords a delicate, almost sacred moment. Outside, the characters’ survival depends on physical exertion and mental stamina, on stealth and luck and the disavowal of pain. Like the two women, I, too, seized the opportunity to weep.

In its representation of the humanitarian crisis at the southern border, “American Dirt” is as powerful as last year’s “Lost Children Archive,” by Valeria Luiselli, though the two novels have fashioned their storytelling from very different cloth. Luiselli’s innovative narrative encompasses history, philosophical fragments, elegies, quotes, bibliographies, photography — beautifully woven layers of complexity. Cummins’s straightforward account relies on intimate, relatable realism.

Lydia’s blind spots come from her desire to maintain her way of life, as a middle-class mother who owns a bookstore in Acapulco. Even though her reporter husband publishes articles about drug cartel violence in “the deadliest country in the world to be a journalist, no safer than an active war zone,” and even though the children of Acapulco, “rich, poor, middle-class, have all seen bodies in the streets. Casual murder,” Lydia has become accustomed to believing that it wouldn’t touch her.

Before the mass murder that compels her to escape the only homeland she’s ever known, her relationship to the plight of migrants is one that many of us would find familiar. “She heard their stories on the news radio while she cooked dinner in her kitchen . . . and she felt a pang of emotion for them. . . . That pang Lydia felt had many parts: it was anger at the injustice, it was worry, compassion, helplessness. But in truth, it was a small feeling, and when she realized she was out of garlic, the pang was subsumed by domestic irritation.”

That she and her son become desperate migrants transpires in part because of her husband’s profession. In a particularly awful display, his killers affix a sign to his chest: “TODA MI FAMILIA ESTÁ MUERTA POR MI CULPA” (“My whole family is dead because of me”). But they also end up on their treacherous journey because of Lydia’s friendship with a bibliophile named Javier, who is charming and affectionate and who happens to be the head of Acapulco’s leading cartel. The night after the murders, Lydia and Luca huddle together in a hotel. The next morning, a delivery boy brings a padded envelope containing Gabriel Garcia Marquez’s “Love in the Time of Cholera.” It’s a chilling gift from Javier, confirmation that he orchestrated her family’s murder. Yet it’s nearly impossible to reconcile this appalling truth with the man who stood in her bookstore and spoke lovingly about literature with her.

At times I wondered if the connection between them, which plays out as a sort of cat-and-mouse game throughout the novel, felt too much like a clever contrivance. But the origins of their friendship as literary soul mates did make me think about the wistful stock many of us bookish types place in literature, our desire to believe in its virtuous influence. “American Dirt” offers both a vital chronicle of contemporary Latin American migrant experience and a profoundly moving reading experience. If only we could press it into the hands of people in power. If only a story this generously told would inspire them to expand the borders of their vision of America.

Polly Rosenwaike is the author of the story collection “Look How Happy I’m Making You.”

Jeanine Cummins will discuss her book at Politics and Prose, 5015 Connecticut Ave. NW, on Jan. 22 at 7 p.m.

American Dirt

By Jeanine Cummins

Flatiron. 400 pp. $27.99