A small sedan pulled up to a run-down motel in Tijuana just before midnight, and a middle-aged Korean American woman behind the wheel ordered You Mi Kim into the backseat.

It was time to "jump" over the border.

Since arriving from South Korea four days earlier, You Mi had been holed up in the motel, waiting to slip into the United States and start what she had been told was a high-paying hostess job in California. She hoped to earn enough to get her out of the $40,000 shopping debt she had recently piled up while a university student.

You Mi had not anticipated an illegal border crossing when she signed up for the job. Worse, she didn't know that she was a pawn in an international sex-trafficking ring -- and that someone was waiting in the United States to buy her.

You Mi got into the car. The driver headed north toward the checkpoint, blending into the 24 lanes of idling traffic inching toward the United States.

Unbeknownst to You Mi, the driver was a "jockey," hired by South Korean sex traffickers to drive women through the busy San Ysidro checkpoint with fake travel documents.

It was February 2003. By then, agents with the U.S. Department of Homeland Security were already on the lookout for Asian drivers, after recording an unusual spike in Koreans coming through border crossings in California, Texas and Washington state.

It was another sign that Asian sex-trafficking networks were becoming increasingly global, branching out from the shadows of sex tourist hot spots in Bangkok and Seoul to install big operations in American cities, particularly Los Angeles and San Francisco.

If You Mi were discovered, agents would handcuff her and take her to a holding cell beneath the road. They would take her fingerprints and deport her.

About 300 feet from the yellow Border Patrol booths, You Mi felt eyes on her.

Roving agents with long screwdrivers, flashlights and guns approached the Korean women in the long line of travelers. You Mi tried to focus her gaze on vendors selling sombreros, guitars and frozen fruit-juice bars to passengers in the cars.

The agents leaned through the window near You Mi.

"I.D.! I.D.!" they demanded. She froze, forgetting the information on the fake visa given to her by sex traffickers masquerading as job brokers.

One agent ordered You Mi's driver to pull out of line for a more thorough search in the secondary inspection portico, near the deportation processing offices.

You Mi watched in terror as agents ordered passengers out of the cars ahead of hers to search their luggage and travel papers.

While waiting, You Mi's driver made a cell phone call to the trafficker who had delivered You Mi to the Tijuana motel.

"Is she still carrying the visa?" he asked.

"Yes, we have it," the driver said.

"If possible, get out and run back toward Mexico. Is there someone watching you guys?"

The driver hung up in a panic. She was cursing herself for accepting a job that she thought was easy money. By now, You Mi was crying with fear.

You Mi's driver ignored the broker's advice. She turned on the ignition. Slowly, she pulled out of the secondary area and headed for the United States. She chose the only exit booth with a female guard, and drove through with nonchalance, as if she had been given clearance to go. Nobody stopped them.

Ten minutes later, the driver pulled off the freeway to a gas station just inside the U.S. border, where a Korean man and a black car awaited.

You Mi had made it to the United States, yet she was anything but free.

At the gas station, the driver took You Mi's fake visa back.

"Good luck," she said, and sped off.

But first, the driver told You Mi, he wanted to stop at a motel and have sex with her.

All the lies and confusion of her journey thus far had You Mi primed for a fight, but she controlled her anger and came up with a strategy. She threatened to report him to the boss if he made any trouble.

Her ploy worked. At 4 a.m., they arrived in Los Angeles, and the man called the boss. Awakened from sleep, he instructed them to go to a motel and call back in five hours.

Although You Mi insisted on two hotel rooms, the driver reserved only one, promising not to touch her.

He slept. She stayed awake, bracing for him to attack her. Finally, the boss called at 9 a.m. and said it was time to meet.

On the way, You Mi got her first glimpse of Koreatown in daylight. There were no high-rises, no neon jungle, no fashion plates crowding the sidewalks. The short, squatty architecture reminded her of South Korea's most outdated neighborhoods. She saw broken-down cars in front yards, garbage in the gutters and homeless people passed out in doorways.

The room-salon sex bars common to South Korea were there, only tucked away behind barbershops and other stores, accessible only to those in the know. There were no glass windows with women on display, like those in You Mi's hometown of Busan. Rather, the women were advertised in the free Korean-language newspapers available on nearly every corner in Koreatown.

Koreatown's sex industry pulsed just as strongly as Busan's, but you couldn't see it from the street. Most of the women in Los Angeles worked in something called an Asian apartment massage parlor, a scaled-down, secretive version of a brothel, where a trafficker operates a massage parlor out of an apartment with one or two masseuses.

At a coffee shop, You Mi looked at her new boss -- round face, round stomach and pudgy fingers stuffed into gold rings. He said she owed him $11,000 for her journey -- $4,000 more than she agreed to in South Korea.

You Mi was tired, beaten down. But she figured that she would be making money pretty fast, so $4,000 more wouldn't be too much of a burden. She agreed.

The boss brought her to an apartment in a cream-colored building with palm trees out front. He told her that she would be sharing an apartment with women who worked for his wife's underground company, Jenny Outcall, which sent women in unlicensed Korean taxis to meet with men who called for sex. He assured her that her hostessing job would be different.

Even though You Mi had to share a bedroom with two other women, the apartment seemed enormous compared with her family home in South Korea. She had never seen a home with two bathrooms, and was awed by the view of the hills from the balcony.

Finally, she was a woman on her own in the big city. Although she'd had some bad experiences on her trip, she felt she had gotten through the worst of it and was finally going to begin correcting the mistakes of her youth.

She changed into a skirt suit to get ready for job interviews. She used makeup to try to cover her acne, which had broken out from the stress of the trip and her money troubles. Her boss drove her to meet several room salon owners, but they all turned her down, saying she was too awkward, too nervous, too pimply.

The boss sent You Mi to a dermatologist, and added the $500 worth of acne creams to her debt.

After four days, he let down the hammer, telling You Mi she wasn't going to find a job in a room salon with her acne and her naivete. He offered her a job in his wife's outcall service, and warned You Mi that she was getting into serious debt trouble and needed to figure something out fast.

You Mi felt queasy. The thought of outcall work terrified her. In South Korea, she had had only a few clumsy sexual experiences with boyfriends, so she didn't know what the men would want her to do.

After weeks of ignoring the warning signs, after hoping against hope that the job she signed up for was nonsexual, You Mi was forced to accept the truth. She sobbed.

Her credit card debt was $40,000 and her trafficking debt was $12,000, and she had no money to get back to Korea. She didn't want to burden her family for a bailout. She didn't even know where she was in California, or who could help her.

An outcall worker sharing the same apartment with You Mi, a 28-year-old married woman on her third trip to the United States for sex work, held You Mi to comfort her.

"Why are you here?" she asked, confused by You Mi's turmoil.

You Mi explained she thought she'd be pouring drinks as a hostess in a Korean room salon, making lots of money.

"What if I don't pay my debt?" You Mi asked.

"If you go back, they will try to find you. ... Things may not get better for you," the woman warned. "I make $15,000 in a month -- so you will be here for only three or four months and you can get out. Think only of that."

She walked back to the elevator. But she couldn't press the call button, either.

Where would she run? How would she repay the criminals, the credit card company? How could she face her family if the house got taken away?

You Mi retraced her steps. She took a deep breath and knocked. A Korean businessman in his 40s with a forgettable face opened the door.

He was wearing a towel.

"Bop mu gut ni?" he said, using the common Korean greeting, "Have you eaten rice yet?"

Trying to stall him, You Mi said she needed to take a shower.

Under the water, she started to tremble. She stayed in the bathroom for 10 minutes, cutting into the hour he had purchased. Fearing her dawdling would raise his ire, she finally emerged in a towel, and sat on the bed.

He noticed she was shaking.

"How long have you been working?" he asked.

You Mi told him the truth, hoping he would take pity on her and let her go. He listened intently, then gave a four-word answer:

"Don't worry, I'll lead."

You Mi stared at a spot on the ceiling and tried not to move -- or think. It was over in five minutes.

Afterward, he said it wasn't very good, but it had a naive quality he enjoyed. He gave her two $100 bills and told her she could leave early.

An underground taxi driver who worked for the outcall service fetched You Mi just before 10 p.m. and took the $200. Half would go to her boss to pay off her trafficking debt, and the other half went to the outcall service. You Mi kept nothing.

Less than two hours later, the "silver taxi" brought her to the next call, a rundown hotel in Koreatown. When she entered her customer's room, he was snorting lines of cocaine on a bedside table.

He wanted her to get high with him but You Mi refused. She had never used drugs and didn't have any interest in them. He became so insistent that it frightened You Mi, and she called the boss' wife and asked what she should do.

She instructed You Mi to ask the man whether he'd like a different girl sent to his room.

"No, it doesn't matter," he said, "I'm just going to call for a second one after you leave anyway."

You Mi ended the call, and within minutes he was having his way with her.

He was so high, that after 80 minutes, he still hadn't reached orgasm. You Mi was in pain, and pleaded with him to tell her what else she could do to get him to climax. But he ignored her cries.

The savior was her cell phone. The boss' wife called to ask what was taking so long. She relieved You Mi and told the man she'd send a second girl.

You Mi rode back to her apartment in another silver taxi. It didn't matter to her "owners" that she was traumatized and sore -- three hours later she was sent out again. It took the taxi an hour to get to a home somewhere in the Los Angeles foothills.

When You Mi arrived at 3 a.m., there were four men and three women from another outcall service in the home, sharing cocaine and flirting. Two men were Korean American and spoke English, and two were from South Korea and spoke only Korean.

Their intention was to have group sex -- something You Mi had never imagined. They paired up and began to kiss and undress. You Mi whispered to the man with her, asking whether it would be OK if they went into a private room. He, too, was uncomfortable and agreed.

You Mi was delivered home by a taxi at 7 a.m. Back in the apartment, You Mi learned from her roommate that group sex and drugs were common in outcall work.

The woman had a few survival tips:

"Never use drugs with a customer. Follow the one-hour rule. Always use a condom. In group sex situations, close your eyes."

But You Mi couldn't get out. She didn't realize that the way outcall girls pay off their debts quickly is by developing a list of regulars. By flirting, by specializing in various sexual techniques.

Customers said You Mi made them feel uncomfortable. She wouldn't smile. She insisted on using the most formal of the three Korean syntaxes when addressing men, not the casual kind reserved for friends and lovers. She was stiff, detached.

You Mi didn't know what to do. She called her sister, borrowing a call girl's cell phone. The news wasn't much better back home.

Samsung had sent a letter to You Mi's parents, threatening to repossess the house. You Mi's mother had taken out a bank loan to pay off the credit card, but the moneylenders were still calling, demanding tens of thousands.

"You'd better not come home for a while," You Mi's sister said. "Mother is incredibly angry with you. She told the moneylenders you are dead."

By April 2003, You Mi still owed $6,000 to the traffickers. They were getting impatient, too.

So her boss sold her. Another broker in Koreatown bought her for $7,200 -- the amount of her trafficking debt plus interest. The sale added $1,200 to her trafficking debt, and she hadn't even begun to address her $40,000 shopping debt from Korea.

You Mi's new owner drove her to San Francisco, explaining there was a massage parlor near the North Beach strip clubs that accepted only Asian girls with trafficking debts.

His plan was to sell You Mi to the madam for more than $7,200. You Mi would then owe her trafficking debt to the massage parlor. The broker told You Mi that massage work would be good for her because the turnover was faster and she'd pay off her debt sooner than if she stayed in outcall.

The broker made his way toward the flashing peep-show marquees of Broadway, and pulled over by an adult video store. He led You Mi next door to a tiny white awning with two surveillance cameras, and pressed the buzzer on a metal security door leading to a two-story staircase.

You Mi was wary. Once inside, she was horrified. She saw the red lights, women in heavy makeup and lingerie, and immediately thought of the glass house districts of Busan and Seoul.

"Don't leave me here," she begged the broker.

The owner of the massage parlor asked You Mi whether she had ever worked in such a place before.

You Mi, head down, shook her head no.

The owner asked the broker to step into the hallway, and told him she didn't want You Mi. She was too immature and wouldn't be a good investment.

The broker was furious. He drove You Mi back to Los Angeles, hardly speaking the whole trip. The next day, he handed her off to a third broker, a friend in the sex-trafficking ring who owed him a favor.

The third broker, also Korean, said his name was Tony. He drove her to a residential house in Inglewood, a brothel without any signs out front. Its lobby was decorated as an aromatherapy center.

Tony handed her a neon-orange tube top that covered only her breasts and a matching micro-mini skirt, and sped away. The owner of the brothel led her inside.

You Mi's mind raced through what was becoming a familiar cycle of panic:

What should I do? Should I just sit down and refuse to work? Should I run? How would I run? Where would I run? If I escape, what about my debt? Do traffickers really find women in South Korea and kill them?

The brothel had five rooms, each with a bed and a shower. There was a separate, larger shower where women bathed customers.

The owner showed You Mi the kitchen at the end of the hall, and the empty milk carton in the fridge where she was told to hide the used condoms.

"Each customer gets 30 minutes," the owner said.

A second woman scheduled to work that day had called in sick, and men were already lining up in the lobby. The two-minute tour was over.

"You're on your own," the owner said.

It made her think of a surgeon, and You Mi was afraid that he might have a sharp tool with him. She frantically waved her hands and shook her head, saying, "No English, no English."

She saw him smirk and thought that her inability to understand him pleased him even more. He spoke to her in soothing tones, indicating he wanted her to lie down on her back.

You Mi felt him examining her with his fingers like a gynecologist. But nothing about his curiosity had to do with her pleasure. His probing turned rough, increasing to an intensity that brought her incredible pain.

As she pleaded for him to stop, she sensed that he was becoming more excited. Finally, he reached orgasm and removed his fingers.

You Mi had five minutes to wash up at a kitchen sink before returning to the lobby for the next customer. Her body ached.

The men brought pornographic magazines to show You Mi what they wanted her to do. One wanted her to urinate in his mouth. Another wanted to ejaculate on her face. They wanted her to bend in yogalike sexual positions.

Each time she refused, even though she knew she was saying goodbye to a $40-$50 tip and prolonging her life as a sex slave.

But in the war between her dignity and her freedom, her refusals were sometimes the only way she could exercise power over her own life.

By the time her 12-hour shift ended on that April day, she had had sex with 14 men.

She earned $800. She brought it to a nearby coffee shop, where Tony and her two prior owners were sharing some laughs at a table.

Tony took the money, then asked her to describe her first day.

"Painful -- literally," was all she said.

It was May 2003, and You Mi had been working for a month in various Inglewood massage parlors.

When You Mi came in the room, she spotted the money and looked away. One of the cardinal rules in a sex parlor is to never initiate a conversation about money, especially with a new customer who could be a cop.

"How much for a full service massage?" he asked.

She went through her list of safety checks: He wasn't muscular, he seemed nervous and he wasn't wearing underwear -- three signs he was probably a civilian. In fact, it looked like he could still be in high school.

You Mi didn't answer him verbally. She held up two hands.

"100?" he asked.

You Mi nodded.

As she was taking her skirt down, the man hopped off the bed and put his clothes back on. He called for backup on his hidden radio. Back in the lobby, a group of police officers rushed in.

"Don't say anything!" the owner whispered in Korean as the officers led You Mi to the kitchen for a private chat.

They wanted to know where the condoms were discarded. They told her they'd let her go if she confessed.

She said she didn't know. Her dependence on the traffickers was too strong. In her mind, the brothel owner was helping her get out of her financial situation. If she got tangled in the American legal system, there'd be nobody to help her. On the side of the traffickers, she saw a light at the end of the tunnel. On the other, she saw a big question mark.

Her silence bought her a trip to the Van Nuys community police station, one of the few Los Angeles Police Department stations with a female-only holding cell.

It was You Mi's first time in a police station.

A Korean officer approached her and asked in Korean how she came into the country. Mistaking him for a social worker, You Mi saw an opportunity for help. She told him everything, from answering an ad for a hostess to her ordeal in Mexico and her sexual slavery in Los Angeles. She told him she didn't have any immigration papers or documents and had come to the country illegally.

The police didn't have the surveillance resources to deal with sex trafficking networks -- that was a job for the feds -- but they could have referred You Mi to a hot line. A major help center for trafficking victims, the Coalition to Abolish Slavery and Trafficking, was just 15 miles away. Instead, the only thing You Mi got was a charge against her for prostitution.

Tony, her trafficker, came to the station and paid You Mi's $1,000 bail, and added it to her debt. He brought her back to the apartment he provided her in Koreatown, and simply sent her to work in a different massage parlor the next morning.

After she pleaded no contest, a Los Angeles Municipal Court judge ordered her to pay a $1,000 fine, attend an AIDS class and complete 180 hours of community service cleaning bathrooms and doing light typing. The judge told her to "stay away from all massage and aromatherapy businesses or any business requiring a female employee to be alone with male customers."

She would ultimately be saddled with $10,000 in legal fees, after one attorney deserted her and she had to hire a second.

You Mi thought again about trying to escape, but the women sharing Tony's apartment with her warned that the organized crime rings in South Korea would know how to find her parents' house.

She kept working.

But You Mi felt no relief. She had simply exchanged slave masters -- she still owed the moneylenders back home in South Korea. Tony said she was free to go, but offered her continued employment as a free agent in his operation in exchange for a small cut of her earnings.

You Mi turned to the other women in the apartment for advice.

Although it had taken her five months to pay back $19,000 in travel debt, rent and bail money to her traffickers, the women promised that she could pay back $40,000 by working the same length of time in San Francisco. Plus, she still had $10,000 in legal fees to pay off.

Most of You Mi's girlfriends who worked independently in the sex industry lived in Koreatown, but worked in San Francisco because the pay was double the Los Angeles standard. Men were expected to pay from $100 to $150 for sex in San Francisco massage parlors, compared with $45 to $75 in Los Angeles.

Moreover, the women could sleep in apartments above the brothels in San Francisco for a few days at a time, then return to Los Angeles during the rest of the week without anybody knowing they were sex workers.

While Koreatown had dozens of Asian massage parlors, San Francisco was the mecca. The city has 150 licensed massage parlors. Many of them are among the 90 in San Francisco that offer sex with Asian women, according to Web sites where customers rank the parlors and the women inside.

You Mi's girlfriends offered to introduce her to some of the massage parlor owners up north.

You Mi had already had one bad experience in San Francisco, but she feared for her parents' safety in South Korea.

She turned down Tony's job offer in Los Angeles.

"I need to go to San Francisco," You Mi told him.

Tony called an underground taxi for her.

E-mail Meredith May at mmay@sfchronicle.com. STORY BY MEREDITH MAY AND PHOTOGRAPHS BY DEANNE FITZMAURICE CHRONICLE STAFF