Teressa Wall emanates fairy-tale magic. She's blonde and pert, yet an iron will shapes those soft lines. She recently cut her long locks and donated them to an organization that helps children being treated for cancer; the feathery flip she now wears accentuates elfin features and sets off a tiny diamond in the crease of her right nostril — a new asset she describes as a "judgment detector." When we meet at Wingers Restaurant in Ontario, OR, Teressa flashes a brilliant smile with white, even teeth that have never known braces, offering a firm handshake in greeting.

I shouldn't be surprised by her forthright nature. She is, after all, partially responsible for bringing down Warren Jeffs, leader of the polygamous cult called FLDS (Fundamentalist Latter-day Saints — not to be confused with the official Church of Jesus Christ of Latter-day Saints, which cast off polygamy in 1890). Better known is her sister Elissa, who testified against Jeffs last September, having accused him of forcing her into marriage at age 14 to her cousin and abetting her subsequent rape. But it was Teressa who set the stage by repeatedly challenging the FLDS patriarchy over the years, and it was Teressa's testimony that dealt Jeffs a fatal blow. Now it is Teressa who risks losing her three children for having taken a stand.

While the typical polygamist wife is a beribboned woman-child dressed in pastel prairie garb, Teressa, 27, betrays a whiff of modern savvy in her khaki pants, long-sleeve henley, and ski vest. She radiates unusual pizzazz for a single mother who has just worked a full day at an auto-service center. Her children are in tow: tall and sober Jasmin, 9, who wears long, tight braids reminiscent of her fundamentalist roots; 8-year-old Nike, who looks just like his father; and Summer, 5, who asks for ice cream and wants to watch a movie when she gets home — wild pleasures they had been denied until two years ago, when Teressa escaped the FLDS compound in Creston Valley, Canada.

Teressa tells me she used to work at Wingers a year ago — "my first job in the 'wicked world,'" she says, chuckling at the phrase grimly thrown around by the sect's leaders. "One of the regular customers invited me to become a teller at Wells Fargo, so I did that. Now I'm a bookkeeper at a Chevy dealership. The past two years have been amazing. I've grown so much, and I've been really lucky." With whatever free time she has, Teressa likes to read, likes to sing, and likes to learn — all forbidden in her former life.

She takes a sip of her raspberry lemonade. "I barely made it through the ninth grade," she confesses. "When I was 14, people thought I was too rebellious, so they pulled me out of school and sent me away to regain my 'sweetness.'" She looks up and grins. "It didn't work."

After dinner, we travel over icy back roads to her small snowbound ranch house, with firewood stacked near the door and icicles stretching from eaves to porch. In the spare living room there's a huge lighted aquarium with water but no fish. In the bedroom, two lacy camisoles, which would be heretical in a strict FLDS home, dry on a blanket stretched on the hardwood floor. Everything is tidy and shining, typical of polygamists who make the most of what little they have and deeply believe that "cleanliness is next to godliness."

After the children bathe, Teressa combs their wet hair and straightens their pajama tops, speaking respectfully of "Father," who will come tomorrow to take them for a three-day weekend. Summer wonders why Mama and Father can't be together. "Why won't you just put on a dress?" she asks, eyeing Teressa's khaki pants.

With the children in bed, Teressa whispers to me, "They can't understand why I don't just go along with the rules. They don't know that the biggest reason I left was to protect them."

Then she tells me her story, starting with her father, Lloyd Wall, and her mother, Sharon Steed, who was what is known as the "second wife" — Lloyd Wall had another family with his so-called first wife. As such, Sharon worked tirelessly, cooking, cleaning, and sewing for both families. "We were the first family's servants," Teressa says.

The seventh of Sharon's 14 children, Teressa spoke her mind. Indeed, she says, her nose was bloodied and her jaw bruised in the course of standing up for her mother and siblings to the first wife. "It made me so mad, the way they treated her," says Teressa, "the way they treated all of us."

Typically, FLDS followers spied on each other, and someone reported that Teressa listened to forbidden music — which eventually included anything not written and sung by FLDS patriarchs. Sharon feared for her daughter's soul and begged her to discuss her future with FLDS head Rulon Jeffs (the stern, bespectacled FLDS "prophet" and Warren's father, who used to be the organization's accountant). Teressa quickly made it clear that, unlike her sisters before her, she would never marry an old man.

In 1996, FLDS families, including Teressa's, began flocking from Salt Lake City to Colorado City, a desert village situated on the Utah-Arizona border, where polygamists' mansions mixed with small houses beneath the Vermillion Cliffs; Rulon Jeffs had designated it the site where FLDS members would be lifted up to the celestial kingdom at the millennium. Every girl 13 and older had been told that if she didn't marry, she would not be lifted up, but rather abandoned to the horrors of the apocalypse. Already 15, Teressa was resistant to the idea, but cult members tried to bring her around: One early summer day, doped up on pain medication after a root canal, she fell asleep in the car, only to wake up and find herself on her way to a meeting with Rulon and Warren, now a rising force in the FLDS patriarchy — her mother had taken a detour. Once there, Warren avidly lectured and questioned Teressa for over an hour while she sat in silence. "They would use our words against us," she says now. "My only defense was to keep my mouth shut."

Eventually she was exiled for her stubbornness to the FLDS compound in Canada. Teressa gives a wry smile. "Everybody up there knew about me before they even met me" — especially Winston Blackmore, the "Bishop of Bountiful," the charismatic and commanding leader of the compound. He told Teressa that the sooner she married, the better.

"No way," she smiled good-naturedly.

Blackmore didn't smile back. Instead, he sent her to work in a log mill, without pay or warm clothing, on an all-male crew. Six months later, he called Teressa from the backwoods of Sundre, Alberta, to one of his several homes in the beautiful Creston Valley, and he handed her a list of candidates for marriage — with his own name at the top. Teressa protested. Then Blackmore looked her in the eye. "You're going to get married, and that's all there is to it. If you don't choose, I'll choose for you."

Teressa looked around her. Everyone she knew was feverishly preparing for the millennium. All her girlfriends had married in order to be ready for Christ's Second Coming. Sixteen now, and weary of rebellion, with nowhere to run, she consented to marry the innocuous-seeming Roy Blackmore, Winston's nephew and Teressa's own cousin by marriage, just a year older than she. They were wed two weeks later in a ceremony performed by Warren Jeffs. Within a few months, she was pregnant with Jasmin.

By now Jeffs had assumed control of the FLDS. An unlikely messiah with his flat affect and scrawny frame, Jeffs at least seemed a gentler version of his father. But soon he was ordering FLDS members to purge their homes of books and movies, of televisions and CD players. Members were also expected to spend entire Sundays at church, listening to tapes of Warren preaching or singing in his anemic voice. By commandment, photographs of FLDS leaders hung in every living room, supposedly to deter the Angel of Death. Women could no longer wear patterned fabrics, and every dress was made from a handful of designs Jeffs had approved. People were upbraided for laughter — accused of light-mindedness. And when a teenage boy was attacked by somebody's pit bull, Warren ordered that all the dogs in the Colorado City compound be shot.

Things only got worse for Teressa, by now in her mid-20s, as her concern for her children's well-being grew; she knew it was only a matter of time before her husband would take a second wife.

She asked him, "How would you feel if you knew I was going to take another husband sometime in the next few years?"

Roy laughed. "That isn't what we believe."

"Put yourself in my shoes. How would you feel, Roy?"

"That will never happen," he said, invoking the "law of Sarah," which states that the first wife can be involved in choosing her sister-wives, but if she opposes plural marriage, the husband has the right to proceed without her blessing.

Meanwhile, in Colorado City, Teressa's sister Elissa, just 14, had been promised by her stepfather to Allen Steed, 19, a first cousin. Elissa called her sister in distress: She wasn't ready for sex and babies, especially not with the son of her mother's brother. "You've got to stand up for yourself, Lisie," Teressa insisted. But Elissa was too young and scared. Despite Teressa's passionate efforts to rally her sisters and even her mother to stop the marriage, the brethren yanked Elissa out of the eighth grade, and Jeffs wed her to Steed. People decorated their marriage bed with cookies, as if to acknowledge that she was still a child.

The arranged marriage, in which Steed regularly forced himself upon his wife, was such a perversion, such an affront, it eventually galvanized Elissa, in 2004, to leave the FLDS group for good when she was 18; Teressa left a year later, at age 25. Their older sister Becky, a plural wife of the wizened Rulon, had quit the group in 2002, at age 26. (That their oldest brother had already managed to escape the community provided something of an emotional and logistical path for the sisters.) Flush with a sense of freedom, the three turned their attention to their two teenage sisters, who would surely be forced into marriage soon if no one intervened. Desperate to protect them, Elissa overcame her fear of government and law enforcement (endemic to anyone reared in polygamy) long enough to contact a lawyer about what had happened to her; soon after, the Utah attorney general's office got involved. Warren Jeffs was charged with rape as an accomplice, a first-degree felony.

A single mother now, with a meager salary, Teressa didn't hesitate when called to testify. "I couldn't afford to miss work, and I didn't want to be gone from my children. But I knew I had to," she says. In November of 2006, she drove to the courthouse in St. George, UT, for the preliminary hearing. "And as I walked down the hall, I thought, I'm going to testify against the man most of my family believes is the most righteous in the world." Once in the courtroom, her knees began to buckle. There, sitting at the defense table, was Jeffs, wearing that familiar expression of feigned sadness, the pitying look he gave people who he believed were going straight to hell. As Teressa tried to answer the prosecutor's questions, she choked back tears. Then she realized she was letting Jeffs tyrannize her even here, far from his seat of power. Eventually, she regained her composure and her conviction.

"I knew," she says, "that as long as I told the truth, it would work out."

The trial lasted two weeks. On September 17, 2007, when the prosecutor asked Teressa the question that sought to irrevocably establish Jeffs's guilt — "Could Warren Jeffs have stopped this marriage?" — Teressa looked Jeffs in the eye and clearly stated, "Yes, he could have stopped it. But he didn't." The verdict came eight days later: Jeffs was convicted on two counts of being an accomplice to rape; he received two consecutive prison terms of five years to life.

Barely a week had passed before Teressa and her children were cuddling on the sofa watching Happy Feet on TV — "I was so glad to be home, and I just wanted to sit and enjoy my children," Teressa recalls — when a knock came at the door. A portly older man asked her name, then thrust a white envelope into her hands. "My heart hit my stomach. Even before I opened it, I knew it was bad news."

Teressa had subconsciously been waiting for some kind of fallout from her testimony, and here it was: Even though he had initially refused to entertain Teressa's petition, suddenly Roy was aggressively seeking a divorce and full custody. She knew that the FLDS leaders had put him up to it and that they were paying the heavy legal fees. The document demanded that Teressa return her children to Canada and pay child and spousal support. "I lost it," she remembers. "I don't usually cry, but that night I sobbed until I couldn't get my breath."

Teressa's eyes grow moist when she tells me what is at stake. She points to the culture of sacrifice and death that is growing in the FLDS, that threatens to envelop her kids if she loses custody. "Who knows when the Priesthood will decide that everyone should drink something so they can be 'lifted up'? I've had nightmares about that," she says. "I have to protect my children."

But the odds are decidedly against her. She is 27, uneducated, and barely able to cover the rent. Her attorney charges 24 percent interest on unpaid legal bills, which now exceed $10,000. Worse yet, her opponent, the FLDS, is deep-pocketed, with vast business and real-estate holdings, to say nothing of political connections (it is said that Warren Jeffs is still giving orders from his prison cell). And, as Canada has routinely turned a blind eye to the goings-on of the polygamist community, the courts there are unlikely to side against them in a mere custody battle. (When Teressa sought a change of venue, to the U.S., for the court proceedings, she was denied.)

While FLDS leaders typically allow young children to be raised by their mothers if parents divorce, the action against Teressa is meant to punish — and to send a message to any woman contemplating the crime of insubordination. Should the patriarchs succeed in having Teressa's three young children taken away from her, they will silence the wives and daughters of polygamy as surely as if they'd cut out their tongues.

So far, Teressa is the only one of the three crusading Wall sisters to suffer repercussions. For her part, Elissa, whose memoir, Stolen Innocence, comes out this month, has said that she would not have been able to confront Warren Jeffs had it not been for Teressa's flinty belief in justice and her encouragement that Elissa heed the voice inside her.

But it is all about the children now. "I want to give them what I didn't have: a good education and some real choices," Teressa says, steeling herself for the ruinous court battle. "I want them to have at least one parent who can make her own decisions. I want to give them gymnastics and dance and music lessons. I want them to learn to think for themselves."

And what about Teressa — does she want anything for herself?

She gazes down the dark hall toward the bedrooms where her children are tucked in, safely asleep, for now. Outside in the snowy meadow, a coyote howls. "I want what I've always wanted," she says, looking both weary and resolute. "To be a good mother."

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