When Francisco Cantú told his mother he wanted to join the United States Border Patrol, she asked a simple question: “Are you crazy?”

She had a point. Cantú was an unlikely candidate for the United States Border Patrol. He had no law enforcement experience. He was from Arizona but had spent the past few years studying the U.S.–Mexico border in Washington, D.C. A graduate program would have been a natural next step: earn a Ph.D. in sociology or anthropology, do some field work, maybe visit the border a few times a year.

But that didn’t feel authentic. “I didn’t want to go out into the desert as a field trip or a study. I wanted it to be my life,” Cantú says. “I wanted to be in the desert, outside, on the border day in and day out. Other than being a rancher, a drug runner, or a migrant, the Border Patrol are the only people out there.”

So Cantú went back to the desert and joined the Border Patrol. The end result is his first book, The Line Becomes a River: Dispatches from the Border.

In the memoir, the desert is an intimidating but not lifeless presence. People have been moving through and living off the desert for thousands of years, and viewing the border as a desolate place only fuels a sense of distance and otherness. “I was [in the Border Patrol] with a lot of people for whom the border represented the ends of the earth. And I do think that’s a mentality that permeates a lot of Border Patrol agents who aren’t from that part of the country,” Cantú says. “They have that frontier sensibility. A last outpost in the middle of nowhere, a dry barren landscape, a foreign landscape. That permeates people’s thinking.”

The subject matter is literally life and death as Cantú and his fellow agents rescue people in the desert or find the bodies of migrants who got lost and died of dehydration and exposure. The reality of crossing the border and discussions about immigration can become overwhelmingly emotional. Yet Cantú’s writing style is clear and straightforward, never lapsing into sentimentality or mawkishness even when discussing heartbreaking trauma.

Most of the book is written in quick vignettes ranging in size from a paragraph to a handful of pages. Cantú, who won a Whiting Award in 2017 for nonfiction, says the structure of the memoir is “borne from the actual journal I kept during those first couple of years I was a field agent. When I first realized I would need to write about my experiences to make sense of them, one of the first things I did was revisit those journals.”

The short scenes build into a kaleidoscopic overview of Cantú’s years in the Border Patrol. His encounters with countless Border Patrol agents, migrants, families, and other law enforcement officers make up the bulk of the book. Holding the narrative together is Cantú’s documentation of his own struggles with the job.

“There are days when I feel I am becoming good at what I do,” Cantú writes. “And then I wonder, what does it mean to be good at this?”

Cantú doesn’t shy away from discussing the heavy toll the job started to take. Near the end of a long day, Cantú is asked to translate for two young girls, 9 and 10 years old, who were picked up in the desert. The girls are scared, separated from their family, and surrounded by men in uniform. Fellow agents ask Cantú to stay after his shift ends so he can interview their mother, but Cantú has to leave. “As I drove away from the station I tried not to think of the girls, and my hands began to shake at the wheel. I wanted to call my mother, but it was too late.”

All of the tension and trauma manifest in Cantú’s dreams. He wakes up with an aching jaw from clenching all night. He has nightmares where his teeth are falling out, where he’s pawing through severed human limbs.

Before signing up, Cantú knew he’d see misery, find people clinging to life in the hot sun, watch people flee deeper into the desert where they might not be able to find any help. “A lot of people probably enter the Border Patrol because they see people who are breaking the law and they have to stop them,” Cantú says. “I partly looked at it as a humanitarian job.”

Cantú received a six-week EMT training and was able to treat blisters, administer IVs, and provide basic medical aid. Toward the end of his time as a Border Patrol agent in the field, Cantú helped rescue a 46-year-old woman who’d been separated from the group she crossed with. She’d spent two days in the desert by herself and was trying to make it to Phoenix to see her husband.

“I cleaned her feet one at a time with a disinfectant wipe, swabbing the fluid from the edges of her broken blisters and smearing them with ointment,” he writes. The woman gently thanks Cantú and calls him a humanitarian. He shakes his head and says, “I’m not.” This moment has stuck with Cantú.

“The Border Patrol is absolutely saving lives,” Cantú says. “But even when I was doing that work, it was hard to feel really good because at the end of the day I’m still part of the structure that’s sending back people who’ve risked their lives.”

The final third of the memoir departs from the pattern of short vignettes and tells an extended story about “Jose,” a friend of Cantú’s who is an undocumented immigrant.

Jose returns to Mexico to care for his dying mother, but he has trouble re-entering the United States and is detained by the Border Patrol. Cantú sees, for the first time, really, what happens after someone is picked up by the Border Patrol. He takes Jose’s children to the courthouse so they can see their father. He helps the family retain a lawyer. The local community rallies to keep Jose from being deported.

Watching a family struggle through the fear of deportation, the threat of death in the desert, the exploitation from coyotes who smuggle people across the border, and a judicial system that’s straining under the weight of undocumented immigrants is heartbreaking, infuriating, and even, at times, inspiring.

Jose’s story helps bring Cantú, and the reader, to a deeper understanding of his time on the Border Patrol. “Being close to his family transformed my understanding of what my work was and what I was close to,” Cantú says. “I felt like I’d escaped that world, but seeing Jose’s story I realized it was part of who I was and something I wouldn’t escape. I signed up to do a job where all those violences were being enacted by other people and being internalized by me.”

Cantú’s ability to bring out untold voices and stories—from the migrants to the Border Patrol agents—is set to change the discussion about the border. “We need to hear stories like Jose’s,” Cantú says. “And hopefully to hear their stories being told by them and not a middle man like me.”

Cantú also sincerely hopes current and former Border Patrol agents pick up the book. “Let’s say a Border Patrol agent reads this interview and says, ‘Screw this guy, he sounds like an apologist or like he’s on the side of the migrants.’ I hope he actually reads the book,” Cantú says.

Cantú spent more than three years in the Border Patrol and five years writing this memoir. Yet he’s still not done with the border or the Border Patrol.

“Two mornings ago,” Cantú says. “I woke up and realized I had a dream I was on the Border Patrol. Those dreams are like concentric circles from a rock dropped in water; the intervals between the dreams have become further and further apart. I’m not wracked by those nightmares and recurring dreams anymore.”

For years, Cantú has been trying to “know” the border. He’s still not there yet, and he knows he may never get there. “This place, the border and borders in general, are endlessly fascinating to me. I have no need to look away. I still have so many questions and this place is endlessly fascinating to me. I’m newly comfortable remaining here and gazing into this place. I don’t think I’ll ever be far away from here.”

Richard Z. Santos is a writer and teacher living in Austin. His essays, fiction, and interviews have appeared in the Rumpus, the Morning News, the L.A. Review of Books, Nimrod, and many more. He recently completed his first novel.