FLDS polygamists marry one wife legally, and then take on additional so-called "spiritual wives." Spouses of the same husband are known as "sister-wives."
The godfearing polygamists
of Hildale and neighbouring Colorado City, members of the Fundamentalist Church of Latter Day Saints (FLDS) have good reason to be jumpy.
Last week, for the first time in 40 years, the state of Utah jailed a local resident for bigamy. Rodney Holm,
a powerful local police officer, will serve a year in prison. He was also found guilty of two charges of sexual misconduct with a minor.
The communities' church leaders, who have brazenly flouted US law for decades, were astonished by the verdict. These isolated, insular mini-theocracies, 60 miles south of the Grand Canyon, have resisted change for 50 years. Now there is revolution in the air. Perhaps emboldened by the authorities' decision to prosecute Holm, some of the wives who have suffered as a result of polygamous marriages are suddenly speaking out.
Elderly women are revealing that resistance networks of safe houses in Las Vegas and Phoenix have been used to smuggle girls to freedom.
Meanwhile, the large home of the community's leader, Warren Jeffs - known throughout the area as "The Prophet" and also under legal investigation - is guarded by young men who are often armed and interrogate strangers as to why they are there.
Dissident churchgoers claim that girls are granted to men by Mr Jeffs as a reward, and taken away as a punishment. Illegal weddings involving girls of 14 and 15, conducted by Mr Jeffs, are claimed to have been commonplace.
According to fundamentalist Mormon theology, Hildale's male residents need a minimum of three wives to secure a place in paradise. Sisters are often required to marry the same man. Mr Jeffs himself has 12 wives.
"What goes on in that place is nothing less than sexual slavery," says Flora Jessop, the daughter of a polygamist who as a teenager rejected her upbringing. "At 16, after I rebelled, I was given an alternative: a forced marriage or the mental asylum," she claims. "The local police and judges were in cahoots with the church."
Few women in Hildale or Colorado City are encouraged or able to look beyond their tightly controlled circumstances. Absolute obedience to husbands is stressed from childhood. Formal education for girls is curtailed in the early teens. Wives have no access to bank accounts. Newspapers are never seen. Access to television is often banned and always monitored.
"The idea of leaving, to go to an unknown world which you have been taught is evil, is terrifying," said Miss Jessop. "And for older women, there are the children you would leave behind."
In the end she fled Hildale with the help of a woman known in Utah as "Auntie Jennie", who lives in the nearby town of St George and has helped more than 30 girls to escape a polygamous marriage.