Last September, eight months before the Trump Administration announced its zero-tolerance policy for immigrants at the U.S. border, the government separated Mabel Gonzales from her two teen-age sons. The three of them had fled Honduras that summer and entered the U.S. through the desert, in New Mexico. “No one saw us when we crossed the border,” she told me. “I was carrying a bottle of water, and I raised it over my head and started waving.” She was trying to get the attention of Border Patrol agents in the distance. “I was seeking asylum, and I wanted them to know that,” she said. By law, migrants can request asylum after they’ve entered the U.S. But during the summer of 2017, in parts of New Mexico and West Texas, the government was quietly testing out the zero-tolerance policy. Before migrants could make an asylum claim, they were charged with the crime of entering the U.S. illegally and were prosecuted. In the process, those who crossed the border with children were separated from them. The Border Patrol agents who apprehended Gonzales told her that she and her sons, who were thirteen and fifteen, would be released to a local migrant shelter. The next evening, another agent informed them that there had been a change of plans. “You’re a prisoner now,” he told Gonzales. “We’re going to have to take your kids away from you.” She entered criminal custody under the mistaken impression that she’d be reunited with her children once she got out.

On Wednesday, I visited Gonzales at an Immigration and Customs Enforcement processing center in El Paso, where she’s been held since September. It was a strange moment at which to make her acquaintance. Earlier this week, as public outrage over zero tolerance mounted, the Trump Administration announced that it was effectively ending the policy. The government could not find detention facilities to house all the families it was prosecuting. The night before Gonzales and I met, a federal judge in California had issued a strongly worded injunction demanding that the government stop separating families at the border and that it reunite parents and children within the next thirty days. For children under the age of five, the deadline for the government was two weeks.

It’s doubtful that the Trump Administration will be able to fully comply with the order. According to the Department of Homeland Security, of the two thousand fifty-three children separated from their parents at the border since May, only five hundred and twenty-two have been returned to their families. Many of the parents in government custody still don’t know where their children are, and lawyers in West Texas think that the number of separated families is even higher. Some seven hundred children were separated from their parents between October, 2017, and April, 2018, more than a hundred of whom were under the age of four. How many of these families have been reunited is unclear. “El Paso was the training ground for family separations,” Veronica Escobar, a former county judge and a Democratic candidate for the U.S. House, told me this week. “What that means is that there probably are more children who are lost in the system.”

For the past nine months, Gonzales has been an anguished witness to the zero-tolerance policy, from start to finish. She has met dozens of mothers who were also separated from their children, including ten women who have been detained in the same facility since last year. In her first few months in detention, she told me, a few women arrived with questions about their children’s whereabouts. By the spring, the scale of the new policy was becoming apparent. Since April, according to Gonzales, about twenty women in the facility have been deported without their children. Each week since then, more women who were separated from their children have arrived. “I kept seeing mothers in here crying and asking why their children were taken from them,” she said. “I cried with them, and I told them, ‘Someone will come and help us. I’m going to make sure of that.’ ”

Gonzales was a pastor in Honduras, and her quiet, dignified manner has helped calm the other women in detention. In late April, she decided to start documenting their cases. “We’re not allowed to have notebooks,” she said. “We’d ask for individual sheets of paper.” At first, she took down the information of a few women in her section of the facility. Then, in the mess hall during lunch, she stealthily distributed sheets to women from the other cell blocks. Some of them were wary of sharing their personal details, but others trusted Gonzales, calling her, reverentially, “la pastora.”

Over the next few weeks, Gonzales gradually compiled the entries in a clean script, on lined paper. Each woman’s name was listed, followed by her detainee number, country of origin, and cell-block number. Below every name was a note about the identity and age of the woman’s children. “I came here thinking I was going to see my children,” Gonzales told me. “That’s what I was told, and the other mothers thought so, too. Everyone thought that. It was a lie. I finally realized that no one was going to help us find our kids. We’d have to do it on our own.”

On May 20th, Gonzales gave the list to a Franciscan sister named Mary Kay Mahowald, who works for the Las Americas Immigrant Advocacy Center, in El Paso. Mahowald makes frequent trips to the detention facility to comfort women and to refer them to the center’s legal team. She started visiting the women on Gonzales’s list, getting basic information about their cases and having them sign waivers so that lawyers could follow up. “I met one woman, a Guatemalan mother, who cried for the whole hour we talked,” Mahowald told me. “It was hard, but I had to keep it together. I had to the get the information.” Some of the women have been too traumatized to trust her. “One of them said to me, ‘What am I signing? Are you trying to keep my child?’ ” she said.

Las Americas is a small organization with limited resources. Linda Rivas, its executive director and lead attorney, told me, “I want to be able to help every single client in detention, but how can we? We decided to focus our efforts on this list. These were women who were crying out to us for help.” In addition to Rivas and Mahowald, the team consists of two assistants, a volunteer, and a newly hired intern. As they worked their way down Gonzales’s list, Gonzales was mailing new documents to the Las Americas office. (She also sent the list to local immigration lawyers, elected officials, and officers at ICE.) When I met Mahowald, on Wednesday morning, she showed me an envelope that had just arrived; in the top left corner, Gonzales’s full name and detainee number were listed as the return address. Last week, the list had ten names on it; now it had fourteen.

When families were separated at the border under zero tolerance, the parents and children were placed in the custody of two separate federal departments, with different processes governing how to release them. The Department of Health and Human Services, which is in charge of the children, needs to vet a parent or guardian before releasing a child. The process takes time and forces parents to produce documented proof of their relationship. “The government is vetting the same parent that it has taken the kid away from,” Rivas said. The Department of Homeland Security, which is in charge of the parents, has the ability to release the detainees with an ankle monitor or a future court date, but it seems unwilling to do so. Over the weekend, D.H.S. issued a statement describing how it planned to reunite families. It called the approach “reunification and removal”: the idea was to unite parents and children so that they could be deported together. Parents with pending asylum claims now face a choice: they can remain separated from their children while waiting for a court date—which could be several months away, at least—or they can withdraw their asylum claim in order to be reunited with their children sooner and face deportation together.

A Crisis at the Border More coverage of the Trump Administration’s immigration policy from The New Yorker.

Because Gonzales has been in detention for so long, her children have already been released to a relative living in the U.S. It’s expensive for her to call them from inside the facility—eighty-five cents per minute—so she speaks to them once a week, usually on Sundays. “I feel empty when I don’t hear their voices,” she told me. Her body shuddered while she spoke about them, and she cried without removing her eyeglasses from her face.