Editor's note: This story is the second in an occasional series looking at the violence tied to Mexican drug cartels, their expanding global connections and how they affect people's daily lives. The first article in the series appeared Jan. 15.
Mexico City (CNN) -- The blue plastic envelope is packed with papers: security camera photos, cell phone records, business cards and letters asking for help.
"My folder, this is my son," Alfonso Moreno says.
The young man left Mexico City on a road trip to Texas last January. His parents say 33-year-old Alejandro, a computer systems engineer, vanished just an hour away from the U.S.-Mexico border.
They have been searching for him ever since.
On this day, a wood-paneled meeting room at a Mexico City peace foundation is the next step in their hunt. They sit at a table with parents of a street performer, a real estate agent and a group of gold salesmen.
A year ago, they all were strangers. Now, they greet each other like old friends, with smiles and warm embraces.
A brutal drug war has brought them together.
Their children are among more than 5,300 people who have gone missing in Mexico since President Felipe Calderon began a crackdown on cartels five years ago, according to the country's National Human Rights Commission. Officials fear the total number could be far higher, because many disappearances go unreported.
The drug war's mounting death toll grabs international attention, but forced disappearances are one of the most troubling problems that Mexico faces, says Rodrigo Escobar Gil, a human rights representative for the Organization of American States.
As the number of cases grows, Moreno and other parents of the missing have become vocal members of the country's high-profile Movement for Peace with Justice and Dignity, which has staged nationwide protest marches demanding a new drug war strategy, better treatment of victims and greater efforts to find the missing.
Hope that their loved ones may be found alive fuels their fervor.
Moreno says he and his wife, like many who are frustrated by sluggish responses and scarce results from officials, felt forced to launch their own investigation. Their search for clues has taken them from the quiet confines of their gated community in Mexico's capital into some of the country's most dangerous areas.
"I have more than the authorities do," he says. "Unfortunately, organized crime is organized. Our authorities aren't."
Retracing the trail
This is what Alfonso Moreno knows: His son Alejandro climbed into a red Mazda 3 and left Mexico City at 7 a.m. on January 27, 2011. Late that night, he planned to reach Laredo, Texas, visit a friend and pick up a new computer.
Alejandro never made it to the border. He disappeared. So did his car.
But he left a trail. A systems engineer for IBM and lifelong technology lover, he sent regular updates throughout his journey, firing off text messages and posting details about his location on Foursquare and Facebook.
"I just passed the Tropic of Cancer," he wrote on Facebook as he drove through the central Mexican state of San Luis Potosi.
A few hours later, another status update compared rush hour in the northern industrial city of Monterrey with traffic jams in the nation's capital.
Just before 7:30 that night, his mother sent him a text message: "Where are you, son?"
"I'm in Monterrey," he replied.
At 8:55 p.m., he posted on Foursquare that he was at a toll booth 107 kilometers (about 65 miles) away from the industrial city, in the town of Sabinas Hidalgo.
Just after 9 p.m., he posted his location again. There was no message -- just his coordinates. His parents suspect he sent them when he spotted something suspicious along the highway.
He hasn't been heard from since.
Time and time again, Alfonso Moreno and his wife, Lucia Baca, have flown to Monterrey and retraced their son's path. But they can only go so far. Officials have warned them to stay out of nearby towns in the area, a stronghold of the Zetas drug cartel.
"I wanted to go looking for him," Moreno says, "but the authorities told me, 'No, if you go in, you won't come out.' "
This is what the father keeps in his blue folder: a grainy toll booth security camera photo that shows his son's hand, reaching out to pay 186 pesos in Sabinas Hidalgo, Nuevo Leon. Business cards of lawmakers, journalists and human rights organizations who've listened to the family's story. Pictures and descriptions of others who disappeared the same way -- driving on highways near the northern city of Monterrey.
He knows their stories as well as his son's. Off the top of his head, he rattles off the dates they went missing.
This is what Alfonso Moreno said when he met their families: Go to the toll booths now, because they only save the security camera photos for two months.
A growing problem
In October, Mexico's president said the "very high" number of missing people was a growing concern. He listed them among the victims of violence that he described as "open wounds" in Mexican society.
"We don't know the size of the problem," Calderon said during a speech inaugurating a new prosecutor's office aimed at helping victims.
"There are different statistics," says Gil of the Organization of American States' Inter-American Commission on Human Rights, "but what is certain is that this is a massive phenomenon in which a very high number of people are victims of this scourge. ... It consumes family and friends and the whole community with anguish and uncertainty."
Mexico's Movement for Peace with Justice and Dignity has documented 600 recent cases of "forced disappearances" as demonstrators from the group travel across the country, protesting violence and collecting victims' stories.
There are thousands more, says Valentina Peralta, who keeps track of information about victims' cases for the movement.
For every death reported, she hears of at least eight other disappearances. But fear stops many from turning to authorities for help.
"They tell us, 'We don't want to file a complaint, because they'll kill us,' " Peralta says.
Some who do go public have managed to wrangle meetings with Calderon and other top Mexican officials
"Thanks to the movement, doors have been opened," Moreno says. "We are no longer invisible victims."
But the burdens they carry are often hidden from view, masked by the steely determination of their fight for justice.
A father closes his family business. A mother eyes the world with distrust. A grandmother fears for her grandchildren's future. For Moreno, old friendships faded. Acquaintances find it too difficult to ask about a missing child.
"A family of pain has been born," Moreno says. "All, all, all hope and pain."
A father's financial struggle
Melchor Flores Landa used to buy and sell homewares in the town of Nextlalpan. Now his search for his son and protest marches against the drug war consume his life. His business is shuttered, and money is tight.
Pain is the only constant. Everything else is in flux -- mentally, physically and financially.
"It's like a waterfall, all going down," he says. "You don't know when you're going to reach the bottom."
Like the Moreno family, his son disappeared in the Monterrey area. He travels the 10-hour bus ride there as often as he can, searching for information. He says his son, a street performer known as "The Galactic Cowboy," hasn't been seen since local police detained him three years ago.
Flores worries authorities will forget about the case if he doesn't show up in person. It costs thousands of pesos (hundreds of dollars) every time he makes the trip.
One recent afternoon, his young daughter asked for 80 pesos ($6) to buy a book.
"I didn't have enough," he says. "If I give her the money, I can't come here."
A grandmother's fear for the future
When Maria Herrera Magdalena gives her grandson a bath, one thought passes through her mind. He is just like his father -- the way he moves, the words he says.
But for this grandchild and several others, having a father is a distant memory.
Four of Herrera's eight children disappeared on gold-buying trips -- a business for which their small town of Pajacuaran in the central Mexican state of Michoacan is known. Three of them left behind young children who still cry out for their fathers.
"To this date they don't understand what's going on. They think they were abandoned," says Herrera, 63. "We haven't wanted to tell them yet. The truth is that I don't feel strong enough."
Fear has taken her sons' place -- at the dinner table, on the street.
Herrera suffers from constant pain, but she knows her grandchildren will feel the deepest consequences.
"They are not going to grow up, nor can they be, like other children. We do not know what future we can give them. ... The love and security that a family has, I know that no one can give it to them," she says.
Tears stream down Herrera's face.
"When I start to talk about my sons, I can't stop crying."
A mother's life in limbo
Other members of the peace movement do a better job of staying composed, Herrera says. She points across the conference room to 54-year-old Julia Alonso, whose son, a real estate agent, disappeared while on vacation outside Monterrey in 2008.
Alonso says remaining focused on the search for her son is a struggle for her, too. Sometimes, hatred overwhelms her. She invites no one into her home. She doesn't give information out over the phone. She fears her son's trusting nature may have contributed to his demise.
"It's as if they stole half your life. Now you don't trust people's intentions," she says.
Despite her inner turmoil, Alonso says she's vowed not to cry until she finds her son and learns his fate.
"The only way I stay this way, when there are 10,000 ideas running through my mind, immediately I run somewhere quiet, I breathe, I wait for the light to reach my heart, and I know I have to live," she says.
Searching for her son keeps her going, even in her darkest hours.
"For family members of victims who have died, at least they know that they are dead," she says. "We are anxious. It is a situation of not knowing. ... We are the ones that push the most because we have the illusion that they will be found alive."
Moreno says some authorities have told him that could be the case, suggesting that cartels kidnap people to strengthen their own operations, putting them to work.
"The car will appear on a ranch in the area at any moment," one official in Nuevo Leon state told him, noting that his son's advanced computer skills could be valuable. "They must be using him."
In October, Mexican troops freed more than 60 people in the neighboring state of Coahuila. The victims told authorities they had been abducted in various locations throughout the country and forced to work for drug gangs.
Reports of unmarked mass graves have also become increasingly common in the region.
A year after his son's disappearance, Moreno says authorities haven't come up with any leads. He and his wife are waiting for answers, and praying that their son will be released by his captors.
"We don't lose faith," he says. "We don't get tired of looking."
His wife smiles and hugs friends as the meeting draws to a close. Moreno holds the blue plastic folder in his hand.