This story is based on official statements from Peruvian police, hours of interviews with family members and friends of Carla Valpeoz, and previous CNN reporting.

(CNN) Shortly after his daughter Carla went missing in Peru, Carlos Valpeoz left behind his old life as a contractor in the Texas Hill Country and boarded a plane to find her. He brought only a backpack with him, unsure how long he'd be away from home.

Valpeoz, 71, conducts himself with relentless force, but his eyes and the weight he's lost reveal his exhaustion. When he talks about his daughter -- his "Carly," his "Carlita" -- his husky, deep voice breaks into sobs.

For nearly six months he has traveled to nearly a dozen small towns in a remote region of the Peruvian Andes called the Sacred Valley. He takes flyers with his daughter's face printed on them and walks from house to house, interviewing anyone who might have seen her. Living on his savings, money from his son and some GoFundMe donations, he's been staying in small hotel rooms and trying to spend as little as possible on food and toiletries.

Carla was on her way to an Inca archaeological site near Cusco on December 12 when she vanished and her family's lives turned upside down.

Carlos Valpeoz takes a break from walking around the Pisac Archeological Park. He has been searching for his daughter in Peru since she went missing.

Her father has traveled across mountains, walked through massive cornfields and searched remote caves looking for her. He's developed relationships with the local police, and even embedded with them to search suspected drug houses.

Along with his son, he has tracked down people who met Carla before she vanished, found the backpack that she left behind at a hostel, requested surveillance footage and tried to request cell phone tower data, only to learn that previous police requests were never completed.

"People need to understand that if they suffer a tragedy like my family has been suffering, they need to know to be prepared for the worst, that they need to take matters in their own hands," Carlos Jr. said.

While the State Department has declined to share exact numbers on how many Americans have gone missing abroad in the past five years, stories of US citizens who vanish in a foreign country have recently made headlines. News outlets have covered the last known moments of a New York couple that vanished and was later found dead in the Dominican Republic, detailed the final conversations that a Florida woman who was murdered in Costa Rica had with her family, and published the travel photos of a North Carolina teacher who was murdered while backpacking in Mexico.

But the quiet struggles of the families of travelers who go missing have gotten less attention.

Chasing her dream in Peru

At 35 years old, Carla is a legally blind woman who has traveled extensively -- in part to show that she couldn't be defined by her disability, and in part to see as much of the world as she could before completely losing her sight.

By December 2018, Carla had traveled to about 20 countries by herself. She had studied Arabic in Egypt, worked with abandoned children in Yemen and traveled to remote villages in Indonesia to advocate for indigenous women. Her family said she had always dreamed of visiting Peru, but she hadn't gotten the chance.

When her friend, Alicia Garcia Steele, told her she was going to travel to Lima to be the maid of honor at a wedding, Carla jumped at the opportunity to go with her. Carla's mom helped her pick out a navy blue dress and a pair of beige ballerina flats for the wedding.

After taking a bus and two plane rides from Detroit, Carla and Garcia Steele arrived in the bustling capital of Lima just in time to help with last-minute wedding details. They would later dance all night at the reception and celebrate Carla's birthday on the beach.

Maria Valpeoz points at the day she found out her daughter Carla was missing.

For the last stretch of their two-week trip, Carla planned to travel alone to hike Machu Picchu, even after her friend advised her not to go by herself.

The day Carla left for her Machu Picchu trip, Garcia Steele grew nervous and kept texting her as the hours passed. She provided CNN with screengrabs of the messages.

"Carla are you there?"

"Carla I'm so worried and have not heard anything from you."

"Is everything ok?!?!"

"Please please please write me when you can."

"Carla. How are you. I'm dying to hear from you."

When Carla replied -- more than 12 hours later -- she apologized, blaming the lack of Wi-Fi and her packed travel itinerary. Garcia Steele was glad to hear that Carla was OK, but something else in that text alarmed her.

"I had a big issue that I need to resolve that I'll do it before I get home," Carla wrote.

This was one of the last times Garcia Steele would hear from her.

Her friends and relatives were unable to reach her for a few days. They didn't panic until Carla missed her flight back to the United States.

Her mom had just moved cross-country for her

Maria, 66, had been living in Detroit for only a few months when Carla traveled to Peru. When Maria retired from her job as a victims' advocate for the Kendall County District Attorney in Texas, Carla asked her mom to move in with her.

Maria suspected her daughter's eyesight was worsening. Carla suffered from cone-rod dystrophy, a condition that causes a person's vision to deteriorate over time. After she was diagnosed at age 10, her mother pushed her to learn Braille and other skills that would prepare her to be fully blind.

Carlos Jr. and his mother Maria, holding Carla's favorite sweater, at his home in Brooklyn.

Carla became very independent, living by herself, walking and biking around the city. She rarely talked about her blindness, and it was even more unusual for her to ask her mom for help.

Within weeks of moving to Detroit to be with her daughter, Maria had learned all aspects of Carla's busy schedule: Her 6 a.m. trips to the gym, her work shift as a docent at the Arab American National Museum, the English as a Second Language classes she taught at a community center. Carla would write her plans on a whiteboard hanging in the entryway of their home, and if something changed, Carla would call her mom.

Carla's excitement about visiting Machu Picchu was palpable in her texts and the sound of her voice.

"I'll be thinking about you when I'm there," Maria remembered her daughter telling her during their last phone call on December 10.

A seasoned traveler quietly vanishes

After the wedding, Carla joined a group of Spanish and Argentinian travelers to hike Huayna Picchu, the steep mountain overlooking the famed ruins, and they returned together to Cusco a few hours later. The group -- still feeling the adrenaline rush -- had dinner together and danced for hours at a club before finally settling at a hostel for the night.

"I can't wait to tell you all about it. It was absolutely worth 100%," she wrote to Garcia Steele in her last message to her on the night of December 11.

While her newfound friends were still asleep the next morning, her family said, a surveillance camera caught Carla taking a cab by herself outside the hostel.

She didn't share her plans with anyone, her family said, but there is no doubt that she planned to come back. Before leaving, she sent a message to a friend saying she would be back in a few hours to hopefully visit some museums. She also left behind two bags with souvenirs, her medicine and her jacket.

Later police would learn that she had taken two cabs. The first driver dropped Carla off at a Cusco street where people ride shared taxis headed to the Sacred Valley. The other driver said Carla was in his collective taxi and that she got off in the valley's first village -- Pisac.

He left Texas behind to search the Peruvian Andes

Carla's father had been replacing the windows of an old home in Comfort, Texas, when he learned his daughter was missing -- three days after she was last seen. He booked a flight to Peru and drove 40 miles to the San Antonio airport to catch an eight-hour flight to Lima. From there, he flew over an hour to Cusco, and a police escort drove him for 40 minutes to Pisac through the curvy mountain roads of the Sacred Valley.

When he arrived in Pisac, he quickly learned that locals don't trust police. He spent days getting to know the residents of the town, and the people who regularly sell handcrafts in the main square and outside the park's entrance. They were and are still cordial with him, but he's not sure if they will ever trust him.

"It has really been a nightmare since the beginning, a total nightmare," he said.

He walked through the narrow cobbled streets of the colonial village looking for surveillance cameras, only to find a handful. Magnifying his exasperation, most of those cameras erase their footage every five days or so.

It had taken police more than a week to track down the information about the cab drivers who had taken her on the journey to Pisac.

What happened to Carla?

A camera outside a drugstore in Pisac captured the last known image of Carla. It shows her walking quickly with her green daypack and her silver folding cane for 14 seconds, about an hour after she left her hostel.

She was heading in the direction of the Pisac Archaeological Park, a 9,063-hectare (22,395 acre) mountainside historic site known for its Incan ruins, tunnels, and massive agricultural terraces.

Carla is seen in surveillance footage from a drugstore in Pisac. It's the last known image of her.

When Carla's dad walked around the village's main square asking about his daughter, a woman selling traditional clothing and an employee of the local tourism information office said Carla had asked them for directions to the park.

A park employee later told police he saw Carla walking toward the entrance, but the park's ticket-taker couldn't confirm that.

For months, police pursued the theory that something had happened to Carla in the park, and that someone had hidden her body, or wild animals had devoured it.

They flew drones over the park, sent in cadaver dogs and rescue teams, but they found nothing, said Peru National Police Colonel Carlos Manuel Valer Cruces, the man leading the investigation into Carla's disappearance.

A team of Peruvian police detectives that handle missing persons and homicide cases are currently working together to find Carla, along with a special prosecutor.

Police now believe that Carla never made it into the park. They believe someone took or lured her to one of the many ritual sites in the region where tourists try an intensely hallucinogenic -- and sometimes deadly -- potion known as ayahuasca.

Carla's family disputes that she would have wanted to take drugs. They believe Carla was sexually assaulted, kidnapped or was the victim of either human or organ trafficking.

"I have no doubt in my mind that my sister was the victim of a crime," her brother said.

Looking for his sister became his second job

Carlos Jr. and Carla -- born 11 months apart -- had the same friends growing up, went to the same schools in Texas and spent hours tubing on the Guadalupe River, talking about their future.

As his dad flew to Peru to search for his sister, Carlos studied maps of the Cusco region and answered dozens of phone calls from people reporting sightings.

"You are not sleeping, you are not eating, you are not showering. You are just working constantly," Carlos Jr., 34, said.

Carlos Jr. holds a reward flyer in the Brooklyn alleyway where he last saw his missing sister in person.

He can't leave his wife and months-old son -- or his job at a design fabrication studio -- indefinitely, but he has traveled to Peru from his home in Brooklyn, New York, at least three times, staying for weeks at a time to help his dad.

"It just never feels like it's enough," Carlos Jr. said.

"It makes you feel rotten inside that you can't grieve, you can't cry, you can't--" he said, sobbing. "You can't be there for your son, for your wife, because you have to do the job of the police."

She's not the only one missing

An ocean away from the Valpeoz family, a woman heard about Carla's disappearance and burst into tears.

Alexandra Ayala Leon, who lives in Seville, Spain, had never met Carla or anyone who knew her. But her own daughter had vanished in the same region of Peru, nearly a year before.

Two men were arrested a few weeks after 28-year-old Nathaly Salazar Ayala went missing. They claimed she had died in a zip line accident and that they dumped her body in a river, yet her body has never been located.

Ayala Leon felt helpless knowing another family was living through the same nightmare.

"I would not want them to suffer the same pain. Unfortunately, they're going through the same (situations) we experienced," said Ayala Leon, 49.

In long phone conversations with the Valpeoz family, Ayala Leon has guided them while they navigate through red tape, deal with calls from shamans looking to take advantage of them and look for experts to help in Carla's search.

She and Alisa Clamen of Canada, whose 22-year-old son, Jesse Galganov, disappeared while backpacking in the Peruvian mountains in 2017, have become like a second family for Carla's brother.

"The pain is the same, different circumstances, but the pain is still there," Carlos Jr. said. "I could never repay them for the amount of love, support and information that they've given me."

Her family feels abandoned

Carlos Jr. has spent countless hours asking US politicians and the State Department to get more involved in finding his sister.

"A lot of times it's really, really tough to get somebody on the other side of the line," Carlos Jr. said. "Sometimes I have to wait days to get a phone call back."

"My family feels like we are just being abandoned," Carlos Jr. said.

US Embassy officials continue telling the family they don't have jurisdiction in Peru to search for Carla.

A State Department spokesperson declined to discuss Carla's case, citing privacy considerations, and said the agency was "aware of media reports of a US citizen missing in Cusco." The spokesperson also referred all inquiries on the investigation to Peruvian authorities.

"When a US citizen is missing, we work closely with local authorities as they carry out their search efforts. The US Department of State and our embassies and consulates abroad have no greater responsibility than the protection of US citizens overseas," the spokesperson said in a statement.

Carla's father walks every other day to the police station in Cusco, trying to make sure Peruvian authorities are actively searching for his daughter. He's shared potential sightings and other tips from locals, but he can't be sure if detectives will act on them.

Valer Cruces, the man leading the police investigation, said that US authorities have not offered local police any specific assistance.

Their lives are changed forever

Soon after Carla disappeared, Maria realized she couldn't stay in Detroit. She started to notice that everywhere she went -- the bank, the supermarket -- people recognized her and they stared at her with sadness. And she imagined she saw her daughter everywhere -- standing at every bus stop, walking on the streets.

A few days after Christmas, she packed a small bag and traveled to Brooklyn.

Childhood photographs of siblings Carla and Carlos Jr. Their mother carries these photographs and a necklace of the Virgin Mary everywhere she goes.

For months, Maria fell asleep every night on the pink couch in her son's apartment, holding her daughter's grey knit sweater.

She can't find Carla herself, she said, but she can support her son and her husband while they look for her. She spends her days making baby purees from scratch and playing with her grandson. She has been paying off Carla's student loans and other bills, and recently had to go through Carla's possessions alone in preparation for selling her house.

Now she's waiting for Carla in a small Brooklyn apartment that her son secured for her. Near her bed, she keeps a pocket-sized velvet picture frame with childhood photos of her children, alongside an image of the Virgin Mary.

Since Carla disappeared, Carlos Jr. has celebrated his wife's birthday, takes any chance he gets to play with his son, and has started a new tradition with his mom: they'll stop by their neighborhood diner to eat cheeseburgers once a week.

"I'm really trying to fill my life with things to do with my family," Carlos Jr. said. "But at the end, I'm always thinking about Carla, the investigation, my dad, my mom. I can't escape it."

Thousands of miles away, Carlos Sr. wakes up every morning before sunrise ready to keep searching for Carla. He doesn't mind wearing the same few changes of clothes for weeks, the sickening altitude or the brutal sun. He'll be right there, far from home and alone, whether someone breaks their silence and calls police, whether his daughter's remains are found, or his prayers are answered and he is able to hug his daughter one more time.

"I need to take my daughter back," Valpeoz said. "I need to find her somehow."