Last week, a young man came to the doors of the Seventy-Two, a shelter for migrants in Tenosique, Mexico, to deliver a message from a local offshoot of the Zetas, Mexico’s most vicious organized-crime group. “What we want is the head of the friar who is in charge of all this,” the man said. “We are going to the shelter today to get all of them.”

The man whose life was in question is a Franciscan friar named Tomás González Castillo. The Zetas want the friar’s head primarily because he runs a sanctuary for U.S.-bound migrants near the Guatemalan border, providing cots, meals, and a few days of safe haven to hundreds of young Central Americans venturing to the U.S. each week. Mostly, these young men and women ride north atop commercial freight trains, facing robberies, rapes, and extortion as they go. Friar Tomás has begun demanding an end to such routinized crimes, calling out the criminal gangs—and, often, the Mexican police—who perpetrate them. The Seventy-Two takes its name from the body count of a massacre that occurred near the U.S. border several years ago; seventy-two migrants were kidnapped by the Zetas, squeezed for ransoms, and allegedly assassinated when they failed to follow orders.

Earlier in the week, Friar Tomás and others at the shelter had lodged formal complaints against local gang members, and as a result, as he put it, “the situation is hot.” Rubén Figueroa, a young Mexican activist with big brown eyes and a thick halo of dark hair, also received a series of death threats. “We have our eyes on Rubén,” cartel affiliates warned shelter members in early March. “Tell your friend that we are going to kill him. Our contacts already know.”

I came to know Friar Tomás and Rubén Figueroa rather closely last fall. For three weeks, I lived beside them on a bus trip across some twenty-five hundred miles of Mexico. The trip had a clear goal: we were accompanying a group of thirty-eight Central American mothers on a search for their disappeared children and husbands, nearly all of whom had vanished while attempting the dangerous journey to reach the U.S., undocumented. Many of the desaparecidos had been snatched up by cartel operatives on the border with Texas or Arizona. Some of the mothers had received ransom calls, turned over their life savings, and waited for their sons or husbands to return, to no avail. Other mothers had come on the trip to search for their missing young daughters who appeared to have been trafficked into brothels by organized crime. Together, we travelled through twenty-one cities and towns in fourteen states of Mexico, visiting some of the most unforgiving terrain of the country’s drug war, looking for signs of hope.

The cartels’ targeting of migrants has become commonplace along the entire route through Mexico, with an estimated twenty thousand migrant kidnappings each year. Most of the time, the victims’ relatives in the U.S. are called upon to cough up ransoms. While the Mexican government has done little to address this crisis, and U.S. immigration policy has arguably fuelled it (by empowering rogue coyotes as a migrant’s best chance of traversing the militarized border), a fearless wing of the Catholic Church has established an underground railroad of sorts to offer migrants protection on their journey.

Friar Tomás is among the most vocal leaders of this movement. Day after day, he led the mothers into morgues, prisons, drug-rehabilitation centers, hospitals, and cemeteries. He stood beside them as they looked through photographs of the corpses of migrants in Saltillo, a dangerous Zeta stronghold, and as they ventured into the Zócalo in Mexico City to beg for help from a non-committal government. Most days, the friar wore a thin straw hat and a long brown robe. On the scorching-hot afternoons when I was sweating and tired and could barely keep up, broadsided by the magnitude of the violence and loss, Father Tomás barely paused for water—hiking alongside railroad tracks, knocking on the doors of shantytowns where suspected traffickers lived, showing photos to passersby and asking, “Have you seen her? Does she look familiar? She’s gone missing.”

Meanwhile, Rubén was investigating leads, pursuing clues despite the many pressures he faces in the course of such work. At one point, we ventured into a particularly violent region where the police wore black ski masks (whether for self-protection or easy impunity, it wasn’t clear); Father Tomás and Rubén alike paid no mind. One day, sitting outside a migrant shelter in central Mexico, Rubén told me, “The death threats are a constant—direct threats, sure, but also indirect threats. For those of us who’ve taken on this lifestyle, we have to be strategically brave, since without our own lives, who else is going to stand up for the lives of migrants?” At the age of sixteen, Figueroa ventured alone to North Carolina and worked in low-wage factory jobs for several years. His struggle in the shadows of the U.S. economy brought him to activism when he returned to Mexico, and he now does the work full-time with the Mesoamerican Migrant Movement, the same group that organized the caravan of mothers.

The threats against Rubén and Father Tomás —which I first heard about by way of Facebook—came at a time when questions of brutality and courage in Latin America were on my mind. Spring began, after all, with a puff of white smoke heralding the first Argentine Pope, a selection that raised dark questions about the new leader’s complicity in kidnappings undertaken by his country’s military junta in the late nineteen-seventies. A week later, in Guatemala, commenced the grim trial of the gray-haired General Efraín Ríos Montt, the former dictator responsible for genocidal crimes in the early nineteen-eighties, including the Army tossing live babies into village wells. Finally, on a different note, the White House announced last week that President Obama plans to venture to Mexico in May, with the topic of “citizen security” reportedly on the agenda for his meetings with President Enrique Peña Nieto. It remains unclear whether that country’s crimes against migrants will surface for discussion, and whether Friar Tomás González will still be alive by then.

The theme tying all this together has to do with moral leadership, or the lack thereof, in the face of unthinkable violence south of our border. What do powerful onlookers owe to the disappeared, or to those who sit on the ledge of becoming so? How does history judge our leaders’ actions in the face of enduring, if not always high-profile, dirty wars?

Strangely, the stories of vulnerable migrants facing cartel kidnappings rarely surface in the domestic debates about immigration reform and border security. What’s more, as the Catholic Church takes a rightful pummelling in many quarters—for its sexual-abuse scandals, perverse gender politics, and insular culture of evasive coverups—it is worth remembering that this other church, too, exists: a risk-your-life church at the heart of Mexico’s drug war, facing down the cartels and the masked police who enable them, and standing with the penniless and powerless. One wonders which Church the new Pope, who took the name of Francis, after the founder of Friar Tomás’s order, will choose to lead.