SAN FERNANDO, MEXICO (NYTIMES) - Ms Miriam Rodríguez clutched a pistol in her purse as she ran past the morning crowds on the bridge to Texas.

She stopped every few minutes to catch her breath and study the photo of her next target: the florist.

She had been hunting him for a year, stalking him online, interrogating the criminals he worked with, and even befriending unwitting relatives for tips on his whereabouts.

Now she finally had one - a widow called to tell her that he was peddling flowers on the border.

Ever since 2014, she had been tracking the people responsible for the kidnapping and murder of her 20-year-old daughter, Karen.

Half of them were already in prison, not because the authorities had cracked the case, but because she had pursued them on her own, with a meticulous abandon.

She cut her hair, dyed it and disguised herself as a pollster, a health worker and an election official to get their names and addresses.

She invented excuses to meet their families, unsuspecting grandmothers and cousins who gave her details, however small.

She wrote everything down and stuffed it into her black computer bag, building her investigation and tracking them down, one by one.

She knew their habits, friends, hometowns, childhoods.

She knew the florist had sold flowers on the street before joining the Zeta cartel and getting involved in her daughter's kidnapping.

Now he was on the run and back to what he knew, selling roses to make ends meet.

Without showering, she threw a trench coat over her pyjamas, a baseball cap over her fire engine-red hair and a gun in her purse, heading for the border to find the florist.

On the bridge, she scoured the vendors for flower carts, but that day he was selling sunglasses instead.

When she finally found him, she got too excited, and too close. He recognised her and ran.

He sprinted along the narrow pedestrian pass, hoping to get away.

Ms Rodríguez, 56 at the time, grabbed him by the shirt and wrestled him to the rails. She jammed her handgun into his back.

"If you move, I'll shoot you," she told him, according to family members involved in her scramble to capture the florist that day.

She held him there for nearly an hour, awaiting police to make the arrest.

In three years, Ms Rodríguez captured nearly every living member of the crew that had abducted her daughter for ransom, a rogues' gallery of criminals who tried to start new lives - as a born-again Christian, a taxi driver, a car salesman, a babysitter.

In all, she was instrumental in taking down 10 people, a mad campaign for justice that made her famous, but vulnerable.

No one challenged organised crime, never mind put its members in prison.

She asked the government for armed guards, fearing that the cartel had finally had enough.

On Mother's Day, 2017, weeks after she had chased down one of her last targets, she was shot in front of her home and killed.

Her husband, inside watching television, found her face down on the street, hand tucked inside her purse, next to her pistol.

For many in the northern city of San Fernando, her story represents so much of what is wrong in Mexico - and so remarkable about its people, their perseverance in the face of government indifference.

The country is so torn apart by violence and impunity that a grieving mother had to solve the disappearance of her daughter largely on her own, and died violently because of it.

Her stunning campaign - recounted in case files, witness testimony, confessions from the criminals she tracked down and dozens of interviews with relatives, police officers, friends, officials and local residents - changed San Fernando, for a while at least.

People took heart at her fight, and found indignation in her death.

The city placed a bronze plaque honouring her in the central plaza.

Her son, Luis, took over the group she had started, a collective of the many local families whose loved ones had disappeared. The authorities pledged to capture her killers.

Scarred by a decade of violence, a brutal war between cartel factions, the slaughter of 72 migrants and the killing of Ms Rodríguez, San Fernando grew quiet for a time, as if spent by its own tragic history.

That is, until July of this year, when a 14-year-old boy, Luciano Leal Garza, was snatched off the streets - the most public kidnap-for-ransom case since Ms Rodríguez's crusade to find her daughter.

Ms Rodríguez's son, Luis, 36, could not help but see the parallels, and wept when he heard the news.

Luciano was kidnapped in one of the family's own trucks, just like Ms Rodríguez's daughter had been.

Luciano's family paid two ransoms for their son, just as Ms Rodríguez's family had in its fruitless attempt to free Karen.

It was all happening again.

Townspeople marched, demanding justice for Luciano.

Brigades searched mile after mile of barren scrubland for signs of him.

His mother, Ms Anabel Garza, charismatic and fearless, became a spokesman for the staggering number of missing people in Mexico - more than 70,000 nationwide - and the unrelenting tide of loss in a country where homicides have nearly doubled in the last five years alone.

But the fight was very different this time.

Ms Rodríguez, whose courage and determination to find her daughter offered a guiding light for the campaign to save Luciano years later, was also a warning of what awaited anyone who pushed too hard.

Unlike Ms Rodríguez's relentless pursuit of her daughter's killers, Luciano's parents did not seek to punish the powerful cartel.

They stripped their hopes to something far more basic - the return of their son.

"Look, we all want to do what Miriam did," said the teenager's father, also named Luciano, on the three-month anniversary of his son's disappearance.

"But look at how things ended for her. Dead."

"That's our fear," he added.

A mother's hunt for her daughter

The walkie-talkie hanging from the kidnapper's belt buzzed repeatedly, interrupting Ms Rodríguez as she begged him to return her daughter.

The weeks after Karen's abduction had become knotted into a single, nauseating progression of calls, threats and false promises.

To pay the first ransom, Ms Rodríguez's family took out a loan from a bank that offered lines of credit for such payments.

The family followed every instruction to the letter.

Karen's father dropped off a bag of cash near the health clinic, then waited in vain at the local cemetery for the kidnappers to free her.

With little to lose, Ms Rodríguez asked for a meeting with members of the local cartel, the Zetas, and to her surprise, they agreed.

She sat down with a slender young man at El Junior, a restaurant in town.

It was 2014, an especially grim time in San Fernando. Many bars and restaurants had closed for fear of shootouts. Mass graves were so common that finding fewer than 20 remains at a time barely merited a headline.

The Zetas, once an armed wing of the Gulf Cartel, had been warring with their one-time bosses for years.

They snatched innocents for ransom to finance their war, or for conscripts to fight it.

Sometimes, they organised death matches between captives for sport.

Luis, Karen's older brother, had moved away to escape the danger. But Karen stayed to finish school and help run her mum's small cowboy apparel shop, Rodeo Boots.

On Jan 23, as Karen prepared to merge into traffic, two trucks pulled up on either side, stopping her.

Armed men forced their way into her pick-up and took off, with her in it.

They drove her to the family home, where Karen lived during the week while Ms Rodríguez, who also worked as a nanny in Texas, was away.

As Karen lay on the living room floor, bound and gagged, a knock came at the door: her uncle's unsuspecting mechanic, who had come to work on the family truck.

The kidnappers panicked and grabbed him, too, then fled.

Now Ms Rodríguez was sitting down with one of them, imploring him to release Karen as his radio squawked sporadically.

He insisted that the cartel did not have her daughter, but offered to help find her for a fee of US$2,000, and Ms Rodríguez paid.

Through the static, she heard someone call him by name: Sama.

After a week, he stopped answering the phone.

Others called, claiming to be the kidnappers. They needed a bit more money, they said, just US$500.

The family doubted it would bring Karen home, but they sent the money anyway.

With every payment, a new hope sparkled for Ms Rodríguez. And with every failed bid to reclaim Karen, she fell further into despair.

Hope is a toxin that poisons many families of the missing.

They either purge it and try to move on from their loved ones, or they sustain it, and it destroys them.

Ms Rodríguez, already separated from her husband, moved in with her older daughter, Azalea.

One morning, a few weeks after the last payment, she came downstairs and told Azalea that she knew Karen was never coming back, that she was most likely dead.

She said it matter-of-factly, as though describing her sleep.

She told her daughter that she would not rest until she found the people who had taken Karen.

She would hunt them down, one by one, until the day she died.

Azalea watched as her mother's sadness hardened into resolve and her hope gave way to revenge.

Her mother was a different person after that.

Luciano's kidnapping

Living in San Fernando means accepting certain realities.

Families have suffered kidnappings and cartel-imposed curfews much as big city residents endure traffic and pollution.

Circumscribed by the violence, many live reduced lives. Hardly a block has been untouched - missing sons, loved ones murdered, houses abandoned.

For a city of about 60,000, San Fernando bears an infamy out of proportion to its size, a misfortune born of geography.

The city lies along a principal route north through the state of Tamaulipas.

Just outside city limits, a cluster of highways untangles, each leading to strategic border crossings with the United States.

Off the motorways, dirt roads in the scrubland provide a web of smuggling routes ideal for traffickers.

In 2010, federal authorities discovered the corpses of 72 Central American migrants at a ranch on the city's outskirts, believed at the time to be the most savage killings ever perpetrated by a cartel.

Then, the following year, rampant abductions of bus passengers led to the unearthing of nearly 200 bodies dumped in mass graves along San Fernando's peripheries.

While many fled to escape the violence, others stuck it out because they had built a life in San Fernando and would not abandon it for the sins of others. Luciano's family stayed.

His grandfather, Luciano, ran a trucking business he started from scratch, and a prosperous cinder block factory. His father, also Luciano, owned a thriving construction materials store.

And at 14, little Luciano helped them both when he wasn't at school.

Like everyone else in the city, Luciano's relatives knew the story of Karen's kidnapping and Ms Rodríguez's tragic heroism.

And they knew their prosperity had made them obvious targets, even more so than the Rodríguez family.

Over the years, kidnappers had already ransomed several members of Luciano's family, including his father, held for 33 days in 2012.

The relatives took precautions, at times monitoring their children with an intensity that bordered on surveillance.

But the kidnappers knew exactly how to strike.

They spent weeks baiting Luciano with a false Facebook account of a young girl.

"You're very handsome," read a message to him from the account. "I would love to meet you one day."

The day came on July 8, 2020, with an agreement to meet briefly in a park. Luciano was watching one of his sisters and couldn't be long, he messaged.

He drove over in a truck that his family let him use to get around town, and within seconds, armed men forced their way in, shoving him to the side and driving off - just as the kidnappers had done to Karen six years earlier.

For the next several hours, Luciano's family fanned out across the city on a manic hunt.

Only after his sister opened his Facebook account did they realise what had happened.

Not long after Luciano was taken, the kidnappers called his father and handed the phone to the teenager.

The first thing he asked was whether his two little sisters were safe.

The following day, Luciano's father deposited a bag of cash on an abandoned dirt road that ran perpendicular to the highway, as Karen's father had. The day after, the kidnappers said they wanted more.

For the second payment, Luciano's father drove two hours and left a bag of cash between two spent tyres at an abandoned gas station.

As he drove back to San Fernando, the kidnappers called. They would deliver little Luciano to the family home that very night. No one slept. Every noise from the street startled them.

By the next morning, the kidnappers stopped answering their phones and the family knew Luciano was not coming home. At least, not in the way they had hoped.

Even then, they weighed the immense consequences of going to the police. But they felt they had nothing to lose.

"The greatest fear one could have as a parent is losing a child," said his mother, Ms Anabel Garza. "And they already did that to us."

The breakthrough

Everyone posts photos on social media, even small-time gangsters. Ms Rodríguez just needed Sama to slip up.

She had already confirmed his involvement in Karen's kidnapping, thanks to the mechanic abducted along with her daughter that night.

The cartel never had intended to keep him, and after they let him go Ms Rodríguez mined his memory for everything he had heard or seen.

She became a social media sleuth, spending countless hours trawling Karen's Facebook profile, looking for clues.

One morning, while stretched across the sofa, she discovered a Facebook photograph tagged with the name Sama.

She recognised him immediately from their lunch, the same slender frame and clean-shaven face.

Standing beside him in the photo was a young woman, wearing the uniform of an ice cream shop two hours away in Ciudad Victoria.

Ms Rodríguez stalked the store for weeks until she knew the woman's hours by heart, and waited outside each shift until Sama showed.

When he finally did, she followed the couple home and marked their address.

But to force the police into action, she needed more than a location. She needed a name. And to get it, she needed to get close.

She cut her hair and dyed it bright red so Sama would not recognise her.

Then she donned a government uniform she had kept from an old, low-level job at the Health Ministry.

With an official-looking ID in hand, she spent the better part of a day conducting a fake poll of the neighbourhood until she got basic details on one of her daughter's captors.

She went to the authorities - local, state and federal - but none would help her.

She carted her files everywhere, like a door-to-door salesperson for whom a "no" was never final.

Eventually, she found a federal policeman willing to assist.

"When she pulled her files onto the table, I had never seen anything like it," said the officer, who remains an active duty commander and asked not to be quoted by name because he had not been authorised to speak publicly.

"The details and information gathered by this woman, working all alone, were incredible."

"She had gone to every single level of government and they had slammed the door in her face," he recalled.

"To help her hunt down the people who took her daughter - it was the greatest privilege of my career."

By the time the government issued an arrest warrant, Sama had already skipped town.

Frustrated, Ms Rodríguez redoubled her efforts to identify the rest of the crew, and before long had a stack of photos of Sama posing with others.

And then, by pure chance, Sama turned up.

It was Sept 15, 2014, Mexican Independence Day.

Ms Rodríguez's son, Luis, was closing down his own shop in Ciudad Victoria to attend the festivities.

He had one last customer, a young, slender man browsing hats. Luis dropped what he was doing to take a closer look. It was Sama.

He called his mother and followed him, careful not to lose him before police arrived.

When they arrested him in the central plaza, Sama kicked and screamed, claiming he had a heart condition.

In custody, he filled in details missing from Ms Rodríguez's investigation, coughing up the names and locations of some accomplices.

One, Cristian Jose Zapata Gonzalez, was barely 18 when police grabbed him, young even by cartel standards.

He was frightened during questioning. As Ms Rodríguez sat outside the interrogation room, the teenager asked whether he could see his mother.

"I'm hungry," he told the officer.

Touched, Ms Rodríguez entered the room and gave the teenager her lunch, a piece of fried chicken, then went to buy him a Coke.

When she returned, the officer asked her what she had been thinking.

"He's still a child, no matter what he did, and I am still a mother," Ms Rodríguez said, according to her friend, Ms Idalia Saldivar Villavicencio, who was with her at the interrogation.

"When I heard him just now, it was like my own child."

Perhaps softened by her kindness, Cristian told them everything.

"I'm willing to take you to the ranch where they killed them and where their bodies should still be buried," he said in his statement to police, referring to the victims of the kidnapping ring.

The search

A decrepit tractor marked the grave at the abandoned ranch, at the end of a dirt road.

Bullet holes pockmarked the outer walls of the adobe house, remnants of a gunfight months earlier.

Mexican marines had killed six of the accomplices, Cristian said in his statement.

Ms Rodríguez picked through the debris left by the kidnappers: grisly stains on soiled tabletops, bones of varying sizes, some mere shards.

A noose hung from the branch of a gnarled tree.

She froze when she found a stack of personal belongings tossed in a pile. A scarf that belonged to Karen and a seat cushion from her truck lay near the top.

Forensic agents claimed that Karen was not among the dozens of bodies they had identified at the ranch.

But Ms Rodríguez fought the government on its analysis, and rightly so.

The following year, the family said, a group of scientists found a piece of femur belonging to her daughter.

Most officials held a grudging respect for Ms Rodríguez, despite complaining about her foul language and pugnacious manner.

"Not everyone got along with her," said Ms Gloria Garza, an official in the state government. "But you respected her mission."

On the drive back from the ranch, Ms Rodríguez passed a barbecue restaurant near the entrance of the dirt road to the ranch.

She had eaten there with Azalea only two days after Karen's kidnapping.

At the time, a neighbourhood resident she knew well, Elvia Yuliza Betancourt, had been seated at a table by herself, sipping a soda.

Ms Rodríguez had said hello and asked whether she had heard about Karen.

By then, everyone had. But Betancourt played dumb, which Ms Rodríguez had thought was odd.

Now, after driving by the restaurant again, it dawned on her: Maybe the young woman knew something. Perhaps she had even been watching the ranch in case the police came.

The dread twisted into rage. She had known Betancourt ever since she was a child, abandoned by a prostitute at the local brothel. She used to give her Karen's old clothes.

Ms Rodríguez raced home and dove back into her research, discovering that Betancourt was involved romantically with one of Karen's kidnappers, who was in prison for an unrelated crime.

Just as she had with the ice cream shop, Ms Rodríguez waited for weeks outside of the prison during visiting hours until Betancourt finally showed.

Police came and arrested her, later discovering that some of the ransom calls had come from her house.

As the months passed, Ms Rodríguez continued to fill her bag with clues she wrung from the case files. But with each passing day, the trails grew more faint.

Some of the culprits were dead, others in jail.

Those still on the street tried to forge new lives as taxi drivers, gas delivery men or, in the case of Enrique Yoel Rubio Flores, a born-again Christian.

Ms Rodríguez went to Aldama, his small home town of about 13,000 people, and paid a visit to his grandmother.

With a heavy sigh, the elderly woman told her that the boy had always been trouble, but at least now he was going to church.

Naturally, Ms Rodríguez began attending service. Sure enough, she found him there.

When police came and arrested him, inside the chapel, the parishioners could hardly believe it, her family recounted.

One asked Ms Rodríguez for mercy. She scoffed.

"Where was his compassion when they killed my daughter?" her family said she had replied.

An awakening

Luciano's kidnapping stirred something in San Fernando.

For the most part, residents don't speak out against organised crime.

The risk is asymmetric. The police are unlikely to do anything, while the cartel almost certainly will - most often in the form of revenge.

Many justify their silence with the belief that victims were engaged in illegal activity themselves.

"They were involved in bad things," people often say to one another.

But the kidnapping of an innocent 14-year-old boy broke the quiet understanding that the cartels had with the people of San Fernando.

And so the family, like Ms Rodríguez, broke the rules that governed how victims usually respond in such cases.

They called on friends and citizens to march with them, to demand the return of little Luciano.

They organised search parties. They gave news conferences.

His mother made a heart-rending recording, pleading with the kidnappers to return her son. Drivers circled town playing it over a loudspeaker.

In August of this year, the family went to Mexico City to pressure the government.

They slept in tents pitched in the city centre and wore ponchos to weather the seasonal storms.

"We don't care about the rain, or anything else," Luciano's mother told local television reporters as her group sheltered under downtown awnings.

"We just want our son back."

The pressure worked. The government dispatched convoys of soldiers, police officers and investigators to San Fernando.

Two to three times a week, they conducted searches.

They traversed the vast expanses of San Fernando's arid edges, but no matter how far they searched, they could never cover it all.

Who knew how many tracts were scored with anonymous graves?

Luis, Ms Rodríguez's son, knew from his own experience that the only way to find a body was to get someone to talk.

For Karen, it was Cristian, the teenager Ms Rodríguez had fed.

Luciano's family had no one. In September, when the state police detained a cartel leader in San Fernando, he refused to cooperate.

And by then, the family knew who the masterminds of the kidnapping were: members of their own family.

After tracing the fake Facebook account, police discovered what Ms Anabel Garza had long suspected - that several of her cousins were involved in organised crime and had teamed up with local cartel members to extort the family.

But by then, the cousins were nowhere to be found. And the searches for Luciano had turned up nothing. They felt almost perfunctory now, performative.

Instead of answers, the family received threats, anonymous calls and messages warning them to stop the search.

Ms Anabel Garza ignored the calls, as Ms Rodríguez had, but the family asked for security from the government.

"Right now, what we are asking for, and what Miriam asked for a number of times, is security," said Luciano's father.

"Are they waiting for them to kill us too?"

A death on Mother's Day

Disappearances undermine the very nature of grief, stripping families of even the most basic closure.

Condemned to a life buoyed by even the tiniest bit of hope, the pain cycles on a loop, its own unique form of torture.

Ms Rodríguez's husband was different after Karen vanished.

Once lively, he now seldom left home. He slowly shrank, physically and spiritually, until his children struggled to recognise him.

For Ms Rodríguez, the pursuit of justice was an escape from the pain. But it came with a price.

Her public campaign threatened more than just a few kidnappers.

She threatened the order of things in San Fernando. Her friends often wondered if she was going too far. If it was only a matter of time.

"I don't care if they kill me," Ms Rodríguez once told Ms Saldivar Villavicencio.

"I died the day they killed my daughter. I want to end this. I'm going to take out the people who hurt my daughter and they can do whatever they want to me."

In March of 2017, nearly two dozen prisoners escaped the penitentiary in Ciudad Victoria, where Ms Rodríguez's efforts had put her daughter's killers.

Worried, she asked the government for protection. The police said they sent periodic patrols by her home and work.

Her family was not satisfied, but she didn't let that stop her.

A month before she was killed, Ms Rodríguez broke her foot chasing down one of the last targets on her list, a young woman who had left town and begun working as a live-in nanny for a family in Ciudad Victoria.

True to form, Ms Rodríguez spent days parked near the family's home, waiting for the young woman to emerge.

She urinated in cups and ran her car battery down listening to the radio in the dark.

Luis said he had to sneak onto the street to give her a jump.

When the police finally arrested the young woman outside the home, Ms Rodríguez tripped as she ran towards them, fracturing her foot.

She was still wearing her cast, and using crutches, on Mother's Day.

At 10.21pm, she headed home; she was once again living with her husband in the small, orange house where Karen once lived.

She parked on the street and lumbered out of the car, moving slowly because of her injury.

A white Nissan truck carrying men who had escaped prison quietly pulled up behind her, according to the police report. They fired 13 rounds.

Her death gave shape to the impunity that twists everyday life in Mexico, and the government scrambled to react.

Within a few months, it arrested two of the culprits, and killed another in a gunfight.

As for the people who ordered the hit, who feared her activism more than they feared the repercussions of killing her, they remain shrouded in secrecy.

Luis obsessed over who they were. But even he had learned the lesson his mother's murder had been meant to impart: only push so far for justice.

"I won't make the same mistakes as my mum," he said.

Though he assumed leadership of his mother's collective, the movement faded in her absence.

Some members left to form their own groups. Others fell into a void of silence, muted by her assassination.

In June of that year, nearly a month after Ms Rodríguez's death, officials in the state of Veracruz, acting with information she had provided, arrested yet another suspect in Karen's case.

The woman had beaten and tortured Karen during the kidnapping, hanging her up like a boxing bag and punching her.

After that, the woman fled to Veracruz, where she drove a taxi while raising her young son.

Ms Rodríguez had found her too.

Not 30m away

Luis arrived late to the funeral, after the procession had already made its way down streets lined with residents watching little Luciano's coffin en route to the cemetery.

At the burial site, as a crowd surrounded the rectangular pit, he stood to the side, weeping.

Authorities found the teenager's body in October in a shallow grave on the northern edge of San Fernando, past a stand of acacia trees.

The killers covered the site with trash to throw off anyone searching. Weeks earlier, volunteers had passed the very spot and missed it.

The government said nothing about how it had found the grave site.

One official claimed that investigators had managed to triangulate the location based on cellphone tower pings.

But that seemed unlikely.

Hours before the body was found, police discovered the cousin who had helped orchestrate little Luciano's abduction in a hospital with a gunshot wound to the leg.

He has since been charged with kidnapping and murder.

Townspeople, long accustomed to looking away in silence, watched the funeral procession crawl through the streets, slow enough for the hundreds of mourners on foot to keep up.

Shop clerks brought them water in the 38 deg C heat.

A mariachi band played as mourners paid their respects at the burial.

The parents' speeches brought tears to the crowd, to Luis and his sister Azalea in particular.

Their sister had died, their mother, too, even their mother's friend, Ms Saldivar Villavicencio, who recently died of Covid-19.

Luciano's father expressed gratitude. He had his child back, in some way.

"I want to thank you for being the perfect son, for bringing joy to all of us every day you were here,'" he said. "You are taking our hearts with you."

His mother thanked everyone for having risked their own safety to help find her son. Family, friends, even strangers.

"You have all taught my family that together we can fight back," she said. "We must rid ourselves of the fear to stand up and speak out."

For Luis and Azalea, it was hard not to hear the parallels with their own mother, buried not 30m away.

She had said as much in her time, words now carved onto a plaque affixed to her mausoleum.

Azalea hugged Luciano's mother for more than a minute, weeping. Luis shook hands with Luciano's father but barely said a word, then walked off, wiping his eyes.

In the beginning, Luis had tried to help the family by introducing them to a police official who had worked on Karen's kidnapping and his mother's death.

But when he suggested that the searches be accompanied by dogs to smell for corpses, the family took umbrage, Luis said.

Those were early days, before they were willing to consider their son might be dead, when hope was all they had.

"We aren't looking for a corpse," Luis recalled Anabel saying.

After that, the trust seemed to be broken, and Luis went his own way.

As the funeral crowd dispersed, Luis and Azalea went to their mother's grave, a church-like structure lined with cypress trees.

Karen was buried there, too, beside her mother.

They knew they were among the fortunate few who at least had somewhere to mourn them.

So many families never found their loved ones. That Karen and Rodríguez now lay together was a small solace.

Luis and Azalea sat for a while as the sun's bite softened, reminiscing in a way they rarely allowed themselves to do any more.

The cemetery emptied, but they stayed, clinging to the moment.