MISSION, Texas — The white-haired priest stepped from the fog like a ghost, his robes and cowboy hat glowing in the predawn darkness like the sandstone chapel that he returns to again and again.

They call this one-room church rising above the banks of the Rio Grande “La Lomita,” the hill. Its plank doors were open earlier this month, as usual. As the man in white entered, the darkness deepened. There’s no light, no electricity inside, just steps from the river.

To the north rises a levee feeding orange groves that perfume the air. To the south, a tangle of chaparral lines the roiling, camo-colored river haunted by Border Patrol agents, smugglers and migrants. A priest once went missing in this brush — his horse found wandering — and he was forever known as the “Lost Missionary.”

The man locals call the cowboy priest is not perturbed by the swirl of shadows in the mist. It’s the chapel he worries about, a 153-year-old landmark that could be sealed behind a border fence scheduled to rise atop the levee in the near future.

It’s where Father Roy Snipes was ordained in 1980. He likes to tell stories about how priests once lived here in a bunkhouse with stables and a blacksmith. To Father Roy — a clean-shaven Santa Claus of a character who drinks Lone Star beer and cultivates a menagerie of pets including llamas and peacocks — La Lomita is more than a spiritual home: It’s a supernatural presence.

The chapel casts a spell on those who enter, he insists. The river winds by with a sacred, life-giving force. A border fence, he fears, would leave both landmarks “entombed” and “desecrated.”

And so, at age 73, he has led the way as church leaders, lawyers and parishioners have joined in fighting the fence. On Friday mornings, he rings the bell atop the whitewashed chapel by hand to summon opponents of the government plan.

Since late October, when the Border Patrol filed a lawsuit in federal court to condemn land around the chapel and begin surveying for a fence, Father Roy has spoken out. He worries it would block access and scare away the faithful, most of whom are Latino. It’s still unclear where the fence would rise, whether it would include a gate, and if it did, how the Border Patrol would control access.

“Maybe they’ll interrogate us on the way out, let the blue-eyed guys go and the brown-eyed guys get questioned,” said the blue-eyed priest.

Border Patrol officials have insisted in court filings that the fence would help secure the border.

In a filing this month, government attorneys insisted that surveying the church’s land would not violate laws protecting religious freedom and that if church officials disagree with the fence in principle, they should take the issue up with lawmakers. It’s too early, the lawyers told the judge, to allege the barrier will affect La Lomita because, “The government has not finalized the nature of any permanent acquisition or how the diocese may be accommodated.”

The Catholic Church has so far sided with Father Roy. His bishop has opposed the proposed fence. Attorneys for the local diocese have attempted to stop it in court, arguing it would violate Catholic teachings, the church’s responsibility to protect migrants and the 1st Amendment right to religious freedom. Lawyers from Georgetown University have helped.

“The church wanted to take a stand early on,” said attorney David Garza.

The next hearing on the government’s condemnation request is Wednesday.

As the legal battle plays out, work on the 25-mile, $1.4-billion fence project — already paid for by Congress — has proceeded. The fence is expected to be built atop the levee just north of the chapel, with a 150-foot “enforcement zone” to the south, which the priest fears will limit access to property owners and law enforcement.

Father Roy measured what he calls the “militarized zone.” He said it would extend on to the church property, across the graves of three of his pets (two donkeys and a llama), “right up to the wall of the chapel.”

This month, four Democratic senators — Charles E. Schumer of New York, Richard J. Durbin of Illinois and Tom Udall and Martin Heinrich of New Mexico — requested Homeland Security Secretary Kirstjen Nielsen disclose how the diocese and other property owners will be affected by the fence.

Some of the priest’s dozen rescue dogs accompany Father Roy to Mass. On Jan. 18, he brought Charlotte, a black lab, and Bandito, a Rhodesian ridgeback mix. They were joined by about 30 locals, enough to pack the rough-hewn pews.

He says Mass here for weddings, and in times of drought prayers for rain. In autumn, he celebrates a mariachi Mass in honor of the Lost Missionary. In spring, he celebrates Palm Sunday with his two pet donkeys and with confessions under the mesquites until sundown.

By comparison, the Friday Mass was spartan. It was the sixth in a series of nine Masses in opposition to the fence, a rite Catholics call a novena. A deacon held a flashlight on the spare wooden altar so the priest could cue his battery-operated CD player. A cowboy trail song commenced with a lonesome whistle that echoed off the bare rafters.

“Move along, blue shadows, move along. Soon the dawn will come and you’ll be on your way,” sang Roy Rogers and the Sons of the Pioneers. “Until the darkness sheds its veil, there’ll be blue shadows on the trail.”

Even the dogs hushed. An 83-year-old Korean War veteran whose parents had sung at Father Roy’s ordination rose to sing. The priest had forgotten his aspergillum, the holy water sprinkler, and used a backup bottle to bless the assembled.

“I always carry a little in my pocket,” he said. “You never know when the devil might come around. You know, he was here last week.”

Father Roy was referring to President Trump, who visited the Rio Grande Valley on Jan. 10 for a roundtable in which he called exclusively on local border wall proponents after having partially shut down the federal government until Congress agrees to fund his border barricade.

“Sister Norma was there, but they say she never got to talk,” the priest said, referring to Sister Norma Pimentel, who runs the area’s largest migrant shelter.

The priest spoke and prayed, as many do here, in a mix of Spanish and English. That’s how he was raised in San Antonio. It’s how he endeared himself to a mostly Latino congregation who call him in Spanish “our father from baptism to burial.”

The priest has also attracted Midwestern retirees, known here as “winter Texans.” Former coal miners and police officers at the chapel who consider themselves political independents say there is no need for a border fence.

“We’re honored to gather here, where so many of our ancestors did,” Father Roy told the crowd. “Watch over refugees and migrants, those separated and searching for a home.”

“You have to respect your brother, whether he has papers or not,” he said. He knows migrants frequent the chapel. They’re drawn by the bells to the sanctuary. Some leave notes in the guest book, praying to receive their immigration papers or to reunite with their children after being separated by immigration officials.

Last fall, Bandito, the Rhodesian ridgeback mix, discovered a group of Guatemalan men cowering at the back of the chapel, below a shrine to the Virgin of Guadalupe. Father Roy gave them water and fried chicken. But when they asked for a ride into town, he knew better. Border Patrol agents park just down the levee, keeping watch. “They’d be on me like a chicken on a June bug,” he figured. Better walk, he told the men. By the time he returned the next day, they were gone.

If the priest was caught with migrants, he worried, he could be charged with smuggling, that agents might lock him up, confiscate his dogs or his battered SUV with its “No walls between amigos” sticker. So he leaves the chapel doors open for migrants, and when he sees them emerge from the river, he’s apt to “toss a blessing over the water.”

The priest grew up idolizing Rogers, Gene Autry and John Wayne, whose likeness adorns just about everything in the church kitchen where Father Roy started his day with machacado con huevo and campfire-black coffee.

“Courage,” the Duke reminds him from a photo on the wall, “is being scared but saddling up anyway.”

Father Roy trained to be a grade-school teacher like his mother. When he graduated from Texas A&M in 1967, a professor urged him to move to the Rio Grande Valley.

He loved the ranch town where he taught. But when he decided to become a priest in 1974, his father — who worked installing heat and air-conditioning systems — warned that he might chafe at the restrictions.

“You come from a long line of rugged individualists,” he said. “And you’re joining the biggest bureaucracy in the world.”

The young priest found kindred spirits in his order of missionary priests, the Oblate Cavalry of Christ. They had traveled the border on horseback in the 1800s, building missions including La Lomita, from which the nearby city of Mission draws its name.

Father Roy first served at a church to the east in Roma, Texas, then at Our Lady of Guadalupe in Mission, which is affiliated with the chapel. As the Catholic Church evolved, Father Roy felt more at home, especially after the ascension of Pope Francis, with his “down-home ways.”

Sometimes, Father Roy wishes he could return to a simpler time. He’ll put on Alan Jackson or Tim McGraw, kick off his boots, maybe watch “The Andy Griffith Show.” He longs for Mayberry, where even a dopey deputy can become a hero.

“I imagine I’m John Wayne,” he said. “But I’m really Barney Fife.”

Years ago, the parish started leasing riverfront land near La Lomita for a summer camp. Some of the children Father Roy hosted grew up to become Border Patrol agents. He still calls them “our boys.” And he still holds “weenie roasts,” bonfires, tugs of war and fishing trips there on a rusty motorboat he calls Ole Blue.

Cruising the foggy river this month, he thought about the people on the Mexican bank, who some Americans demonize and despise. They see the U.S. as a country club to be protected, he said. He sees it as a field hospital for the wounded. He’s as concerned about American hatred as he is about the fence.

“Our problems are much more profound,” he said.

On Jan. 16, he had received a letter from a woman in Arizona who read about his defense of the chapel. She wrote that she hoped migrants would cross the river and kill him.

“And she was a Catholic lady,” he said.

He jokes that she was probably drinking when she wrote him. Maybe she’d regret it when she sobered up. But he knew better.

He’s considering extending the series of Friday Masses at La Lomita, where he returns to pray each day at sunset.

The evening of Jan. 18, he found a full moon rising above the chapel behind a screen of clouds. Cicadas hummed in the mesquite, stirred by a cool breeze. On the nearby levee, a Border Patrol agent had parked his truck, lights blazing.

Father Roy stepped inside the chapel and sat in one of the empty pews. Peace flooded him. He thought about what La Lomita stands for, of the missionaries who came before him and the challenges they faced. He felt sure they would side with him against the government.