Opening the door, he paused to let his eyes adjust from the bright light of the summer day outside before he could see her.

The girl was huddled with a friend on a grimy mattress on the floor, lolling in a methamphetamine haze.

Instruments of modern-day bondage lay scattered about: A drug pipe keeping her in a meth-induced stupor, willing to do almost anything for the next high. A prepaid credit card. Three cellphones, tethering the girls to pimps and johns 24/7.

Dressed up in white lingerie and thick eye shadow, Bobbi Larson was just 17 and a long way from home.

“What’s going on?” she yelled when she heard people in the hall of the Minneapolis bungalow.

Then a man about her dad’s age walked in, shirt untucked over faded blue jeans, head shaved bald, a stubble of beard on his face. There was nothing unusual about that. Bobbi had learned to expect all kinds of men to show up. Rich professionals and blue-collar johns. Men from rough parts of town and those who drove in from posh suburbs, buying sex with girls as young as their own daughters.

He was careful about the tone of voice he used, aiming for compassion. “I’m Sgt. Snyder, Minneapolis police,” he recalled saying. “I’ve been looking for you girls. You guys OK?”

Bobbi hated cops. They could disrupt her ability to get meth and haul her back into treatment.

“We’re fine,” she snapped. “What do you want?”

Grant Snyder knew they were not fine. In 16 years of police work, he had seen too much of the ugly world of underground online sex markets, where girls from all across Minnesota were bought and sold via smartphones and laptops.

Pimps liked to target the particularly vulnerable ones — kids with abuse in their past, autism, fetal alcohol syndrome. When those challenges combined with teenage rebellion, and kids bolted from home to the streets, they were easy prey.

Snyder was fed up with the number of kids being snagged by these pimps, used by the johns. He had ceased to view prostitution as harmless. To him, these kids and even adults trapped in the sex trade were victims pure and simple. They desperately needed help whether they knew it or not.

He had joined an unusual collection of Minnesotans — prosecutors, Catholic sisters, a billionaire hotel company executive, formerly prostituted women, advocates, truckers and cops — who were changing the way prostituted children are treated in the state. In 2011, they successfully pushed for a new state law defining those under 16 as victims rather than criminals. Their efforts had put Minnesota in the vanguard of states intent on dismantling seedy networks of websites, pimps and johns.

The moves to decriminalize and help prostituted children came with a change of language to describe what was happening to them: “Sex trafficking” began to replace “prostitution” even when children were not transported across state or national borders. “Victim” supplanted “prostitute.”

Soon a push began that would raise the age of those regarded as victims to 18 and secure money for programs to help girls escape their predators for good. Some likened the effort to the transformation back in the 1970s in how society viewed domestic abuse, when the first battered women’s shelters opened.

But on this day, in the midst of those broader efforts, Snyder simply needed to get Bobbi and her friend out of that house.

Rooms like the one where Bobbi had ended up in north Minneapolis exist all across the state, police and prosecutors say — in good neighborhoods and bad, in urban areas, suburbs and small towns. The juvenile sex trade respects no boundaries of geography, class, culture, gender or race.

Bobbi hopes that sharing her story and the horrors of what it meant to be trafficked will save other girls from that fate in Minnesota and beyond. She knows she made some terrible choices in her young life and lives with shame, blaming herself for part of what happened, sorry for how it terrified the parents she loves.

Scott and Deanna Larson, the couple who raised her and whom she regards as her mom and dad, are actually Bobbi’s uncle and aunt. They live nearly 200 miles to the north along Lake Superior, running a North Woods bar and grill catering to snowmobilers and cabin owners. Bobbi grew up there, amid the towering pines and craggy boulders lining the shore. A classic Minnesota childhood.

How had she ended up in this dismal room, so far away?

Her parents could only guess. Their beautiful little girl, the one who had been a Girl Scout, a basketball player and a decent student, had gotten in with the wrong friends as a young teen and started experimenting with drugs and who knows what else. She had slipped loose from their best attempts to safeguard her with drug treatment and group homes.

But they never dreamed that their small-town girl might get involved in sex trafficking. When a Sgt. Snyder from the Minneapolis Police Department called to say he thought he had located their daughter, who had been missing for two weeks, and briefed them on what was happening, they were stunned.

Snyder was not. He knew it happened more often than most people could fathom. Though many Americans think of child sex trafficking as a global scourge of the developing world, advocates warn it is an insidious domestic problem, too.

Unlike the past, when pimps paraded girls and women on street corners, sex trafficking in the digital age flourishes almost invisibly online. In just one 72-hour sting over the summer, an FBI-led operation rescued 105 children and netted 152 pimps in 76 cities nationwide, including four alleged pimps in the Twin Cities.

The true scope of the problem is elusive. Reliable statistics do not exist, and estimates on the number of underage trafficking victims range from 1,400 to 2.4 million, according to a September report from the Institute of Medicine and the National Research Council. The National Center for Missing & Exploited Children estimates 100,000 kids a year are victims of sex trafficking in the United States. Many transactions go unreported to police.

In the absence of hard numbers, some say estimates are overblown.

In 2010, the Women’s Funding Network, an advocacy group, commissioned research on how many underage girls were being trafficked in three states, including Minnesota. Based partly on subjective attempts to gauge the age of girls in photographs in online ads, researchers concluded that on any weekend night in Minnesota, about 45 underage girls are exploited through websites and escort services.

Whatever the precise extent of sex trafficking in Minnesota, Snyder understood from experience that too many girls were being harmed. He knew he would have to earn the trust of Bobbi and her friend in order to help them. The odds were not good for extricating Bobbi from the drugs and the way she supported her addiction. But there was something about Bobbi that made him think there might be a chance.

Now, towering over Bobbi and her friend in the meth-infused room, he calmly told them, “You guys are going to have to come with us.”

He leaned down and stretched out his arm to help them up.

A North Woods childhood

Everyone’s life is a stew of good and bad luck. For Bobbi, luck arrived in extremes.

A doctor and therapists would later conclude that before she was even born, alcohol had washed from her birth mother’s blood, through the placenta and into her tiny forming brain.

There, it may have signaled genes to make too much or too little of certain chemicals. It may have tricked some cells into self-destructing sooner than they would have in a healthy developing brain.

Bobbi’s birth mother insists she didn’t drink alcohol during pregnancy and didn’t develop problems with alcohol until her daughter was 6 months old.

It is estimated that each year in Minnesota, 8,500 babies are born already exposed to alcohol. Not all will show effects. On the day Bobbi was born in Two Harbors, Minn., in late 1994, no one could predict exactly what that might mean.

Bobbi’s birth parents, struggling with their own addictions, initially attempted to raise her along with her two older brothers. They lived in a subsidized house near the North Woods town of Finland, Minn., Scott remembers. He and Deanna were so concerned the kids weren’t getting enough nutrition that they dropped off groceries.

That environment also could have affected Bobbi’s young brain. Babies raised in harsh circumstances, where the world proves untrustworthy, develop differently, research shows. They find ways to alleviate stress quickly, not worrying about the future. Studies show they end up with greater chances of substance abuse, teen pregnancy, employment difficulties and decreased cognitive ability.

But at age 2, Bobbi’s luck swung dramatically the other way.

Lake County social service officials were desperately looking to place her and her brothers, now in temporary foster care with another relative, in a permanent home together.

Scott and Deanna Larson decided they should become legal guardians for their niece and nephews, even though they were already busy with 11- and 14-year-old daughters of their own. Deanna worked as a dental hygienist in Duluth. Scott managed the local golf course and served as assistant fire chief in Two Harbors. A salt-of-the-earth kind of couple.

On a cold winter Sunday in 1997, Bobbi was delivered to the Larsons’ front door in Two Harbors. Scott was sitting in a recliner watching football on TV and remembers Bobbi toddling straight over to him, her blue eyes sparkling under wisps of blonde hair. She smiled and climbed right up onto his lap.

They read a book together that evening. Right away, Scott understood his new daughter craved affection.

The Larsons treated Bobbi and her brothers like their own children. All three later took their last name and called them “Mom” and “Dad.”

Scott and Deanna would pack everyone into the family Suburban to go fishing at nearby ponds, to worship at the Lutheran church and to watch high school hockey, volleyball and basketball games. The cheerleaders let Bobbi use their pompons.

Bobbi was a bubbly child, her loud voice and wide smile attracting other kids. In grade school, she earned several perfect attendance pins. She rode snowmobiles and four-wheelers, made up new games and taught her classmates the latest dances. She went out of her way to make her friends happy, bringing one a favorite Pop-Tarts snack every day at school.

She had a sweet, sensitive side. When the Larsons’ oldest daughter gave birth to a son, Scott watched 11-year-old Bobbi cradle, feed and diaper the baby with a tender, maternal touch. The older daughters were in nursing careers, and Bobbi thought she might want to do that someday, too.

Hannah Broadbent, a close childhood friend, recalls Bobbi confiding to her the pain of feeling abandoned by her birth parents.

Several times a day, Bobbi told Scott and Deanna “love you,” then waited to hear them say it back.

They always did.

Signs of trouble

Bobbi’s teachers at Minnehaha Elementary were the first to sound an alarm.

At conferences in the flat, brick school building two blocks from tourists whirring by along North Shore Drive, they told Scott and Deanna that Bobbi’s boisterous personality was becoming disruptive in the classroom.

Doctors diagnosed Bobbi with attention deficit hyperactivity disorder and put her on medication. At age 12, specialists diagnosed her with fetal alcohol spectrum disorder, marking it in her medical records as a “permanent diagnosis” requiring long-term support. Bobbi would need additional time for complex tasks and her family would need to be aware of her “expressive difficulties,” the document said.

All of that could translate into Bobbi having more trouble than the average kid making good decisions, anticipating consequences, controlling impulses or learning from experience. It also meant she might be outgoing, hungry for even negative attention, trusting, randomly attracted to strangers and vulnerable to manipulation — a dangerous mix heading into adolescence.

The timing was tough for Scott and Deanna. Their older daughters were finding their way as young adults. Scott and Deanna were working long days trying to turn a profit at the bar and grill they had just bought.

But the medical predictions kept coming true. As a young teen, Bobbi started getting suspended from school for fighting and smoking cigarettes. Her friend Hannah saw that while Bobbi was influential among her peers, she looked up to and was easily influenced by older friends.

She would brush on dramatic eye shadow and fix her hair, then pop out the screen of her bedroom window in the middle of the night and take off for the breakwater wall, a long concrete bulwark jutting out into the cold, choppy water of Lake Superior. There, she would sit near a small lighthouse with guys 18 and 19 years old, drink cheap liquor and smoke a low-grade form of marijuana they called ditch weed. She started experimenting with sex.

It wasn’t unheard-of behavior for a teen on the North Shore or anywhere else. Nearly a third of Minnesota high school seniors have smoked weed in the previous year and more than half have drunk alcohol. About half have had sex by their senior year.

Hannah saw Bobbi turn into a different person when she was high; she could be mean.

Scott and Deanna worried that their daughter was headed for disaster. Scott would sit in their darkened house trying to catch Bobbi’s friends picking her up at her window. If she didn’t make curfew, he would get in his car to track her down.

He and Deanna explained repeatedly that running around was dangerous, but Bobbi didn’t seem to understand. The fun was too alluring.

Bobbi pushed them too far over the Fourth of July in 2009, when they learned she wasn’t hanging out with the friends she said she would be with. Once again, Scott found her and pulled her out of a car that she had been riding in drunk with older boys.

Scott and Deanna decided Bobbi needed more help than they could give her and made a desperate decision to send her away to treatment. She was 14.

Learning to escape

Northland Recovery Center in Grand Rapids, Minn. was the first stop in a four-year odyssey for Bobbi through treatment centers and halfway houses stretching from Brainerd to Eden Prairie.

Scott and Deanna were involved in decisions about where she would go, but because of their status as legal guardians, Lake County officials also helped decide which programs were the safest, best places for Bobbi.

During the treatment programs, in groups and one-on-one, counselors tried to help Bobbi figure out why she was drawn to using drugs. They guided her in identifying triggers for her urge to get high and in coming up with responsible choices to make instead.

At every turn, Scott and Deanna dutifully drove to visit her and participate in parent meetings, sometimes making three-hour trips to the Twin Cities and back twice a week.

“All of this stuff was all about wanting her to be able to go on to leading a successful life,” Scott said.

They were heartened when Bobbi completed several treatments successfully. She was good at convincing the counselors that her addictions were under control. Later on, she would admit it was acting.

“I was just like, ‘OK, I can just use when I get out. Whatever. I’ll just do [the treatment],’ ” she said. “I’m a very good manipulator, and it’s sad to admit, but I am.”

She also became adept at simply running away. Security at adolescent treatment centers and group homes varies widely. Only three centers in Minnesota are locked facilities, explained Jerry Kerber, inspector general for the state Department of Human Services. Others tailor security and freedom to each child, with the goal of teaching them to make good choices. State licensing standards say facilities need to assess children to see if a locked door is warranted.

Kids in such places are usually stripped of electronic devices that would give them access to the Internet. But in early 2012 — more than two years into her cycle of treatments — Bobbi snuck an iPod Touch into Little Sand Group Home in the northern Minnesota woods near the tiny town of Remer, and cracked into some nearby Wi-Fi. The group home was not a locked facility, although alarms on the doors alerted staff when kids were leaving.

A new friend from treatment plotted with Bobbi how they would run away. They posted a message on a dating website seeking a ride to the Twin Cities. A stranger responded and they made plans for him to pick them up. They were out of the building and into the car in moments.

The friend told Bobbi she knew of an empty house on Kenny Road, just north of Interstate 94 near downtown St. Paul, a place where they could get out of the biting January cold. But when they arrived at the tan, two-story duplex, the doors were bolted shut. They used an old garbage can from someone’s back yard to climb up and boost themselves in through an unlocked rear window. The house was warm, but the bathroom was unusable.

They did their best to clean up the large living room, sweeping the wood floor and washing it with disinfecting wipes stolen from the Holiday convenience store a couple of blocks away. They tacked old sheets to the walls to section it off and moved a box spring and mattress onto the floor. They wrapped their clean clothes over left-behind pillows before daring to sleep on them.

For nearly a month they sank into a drug-induced fog, sleeping until the afternoon, then walking to the gas station to use the bathroom and sometimes steal food before returning to the house to plug in their hair straighteners and put on makeup.

Bobbi said her friend showed her how to get money. They walked toward downtown St. Paul at night and in no time at all men began approaching. They went with them to hotel rooms or apartments to have sex. Sometimes they invited the men to the vacant house.

Bobbi’s friend taught her to make sure to ask for the money before having sex and to use condoms.

Later, Bobbi would tell police that she didn’t want to do it, but she also didn’t want to look weak. She was hungry and desperately wanted a shower — something she could get if she went with men to hotel rooms or their homes.

As the girls were drawn into selling sex in the winter of 2012, the Women’s Foundation of Minnesota had decided to make combatting child sex trafficking a major initiative of the organization. It launched a $5 million, five-year campaign, giving grants to groups fighting trafficking and working with victims, funding research and spreading the word that “Minnesota Girls Are Not For Sale.”

Men already were buying Bobbi.

“Every time after I turned a trick, I felt disgusting,” Bobbi said later. “You know, I felt like, even after I showered, I was, like, ick.”

The money bought them drugs and alcohol, clothes, makeup and manicures. Bobbi met up with members of the Gangster Disciples gang. She agreed to let her friend dip a needle in ink to draw a homemade tattoo of a dollar sign on her chest. It would prove, she thought, that she was worth something.

More than three weeks after they ran away, authorities found Bobbi and a friend swimming in a hotel pool in downtown St. Paul, Bobbi said. She was delivered back to the group home in northern Minnesota.

But by then, Bobbi had developed a dangerous new taste for life on the run.

Read Part 2: Lured by drugs, used by pimps

Go to Part 3: One cop's determination

Go to Part 4: Struggling to find a way forward