Her account reminded me — painfully — of the legend of the Pied Piper of Hamelin. In the story, a piper shows up and asks for 1,000 guilders for ridding the town of a plague of rats. Playing his pipe, he lures all the rats into the River Weser, where they drown. But Hamelin’s mayor refuses to pay him. The piper goes back into the streets and again starts to play his music. This time ”all the little boys and girls, with rosy cheeks and flaxen curls, and sparkling eyes and teeth like pearls” follow him out of town and into the hills. The piper leads the children to a mountainside, where a portal opens. The children follow him in, the cave closes and Hamelin’s children — all but one, too lame to keep up — are never seen again.

Montserrat said that she was moved around a lot and often didn’t know where she was. She recalled that she was in Detroit for two months before she realized that she was in ”the city where cars are made,” because the door to the apartment Alejandro kept her in was locked from the outside. She says she was forced to service at least two men a night, and sometimes more. She watched through the windows as neighborhood children played outside. Emotionally, she slowly dissolved. Later, Alejandro moved her to Portland, Ore., where once a week he worked her out of a strip club. In all that time she had exactly one night off; Alejandro took her to see ”Scary Movie 2.” [correction appended]

All the girls I spoke to said that their captors were both psychologically and physically abusive. Andrea told me that she and the other children she was held with were frequently beaten to keep them off-balance and obedient. Sometimes they were videotaped while being forced to have sex with adults or one another. Often, she said, she was asked to play roles: the therapist’s patient or the obedient daughter. Her cell of sex traffickers offered three age ranges of sex partners — toddler to age 4, 5 to 12 and teens — as well as what she called a ”damage group.” ”In the damage group they can hit you or do anything they wanted,” she explained. ”Though sex always hurts when you are little, so it’s always violent, everything was much more painful once you were placed in the damage group.

”They’d get you hungry then to train you” to have oral sex, she said. ”They’d put honey on a man. For the littlest kids, you had to learn not to gag. And they would push things in you so you would open up better. We learned responses. Like if they wanted us to be sultry or sexy or scared. Most of them wanted you scared. When I got older I’d teach the younger kids how to float away so things didn’t hurt.”

Kevin Bales of Free the Slaves says: ”The physical path of a person being trafficked includes stages of degradation of a person’s mental state. A victim gets deprived of food, gets hungry, a little dizzy and sleep-deprived. She begins to break down; she can’t think for herself. Then take away her travel documents, and you’ve made her stateless. Then layer on physical violence, and she begins to follow orders. Then add a foreign culture and language, and she’s trapped.”

Then add one more layer: a sex-trafficking victim’s belief that her family is being tracked as collateral for her body. All sex-trafficking operations, whether Mexican, Ukrainian or Thai, are vast criminal underworlds with roots and branches that reach back to the countries, towns and neighborhoods of their victims.

”There’s a vast misunderstanding of what coercion is, of how little it takes to make someone a slave,” Gary Haugen of International Justice Mission said. ”The destruction of dignity and sense of self, these girls’ sense of resignation. . . . ” He didn’t finish the sentence.

In Tijuana in November, I met with Mamacita, a Mexican trafficking-victim-turned-madam, who used to oversee a stash house for sex slaves in San Diego. Mamacita (who goes by a nickname) was full of regret and worry. She left San Diego three years ago, but she says that the trafficking ring, run by three violent Mexican brothers, is still in operation. ”The girls can’t leave,” Mamacita said. ”They’re always being watched. They lock them into apartments. The fear is unbelievable. They can’t talk to anyone. They are always hungry, pale, always shaking and cold. But they never complain. If they do, they’ll be beaten or killed.”