(NBC) — Tonight, an all-new two-hour “Dateline” features the behind the scenes story of Rebecca Muser versus Warren Jeffs, one of the FBI’s most notorious fugitives.

Rebecca, a former member of the Fundamentalist Church of Jesus Christ of Latter-Day Saints, opens up about life in the church, having to share her husband with more than 60 other women and why she decided to leave the denomination. Hear from Rebecca’s former classmate Andrew Chatwin, private investigator Sam Brower and more.

Here is a preview of Keith Morrison’s report:

Short Crick is actually the two little towns of Hildale, Utah, and Colorado City, Arizona. The mountain that rises above them is called Canaan. 

Here lived some eight thousand souls — the core, the center — of what they call “the work.” Most people know it as the FLDS, Fundamentalist Church Of Latter-Day Saints. No, not LDS. Regular Mormons were considered ‘apostates’ around here and — doomed for eternity —for the perceived sin of having rejected fundamentalist tenets like plural marriage. Polygamy. The life into which Becky Musser was born.

MUSSER: We were taught you should want to be a plural wife because it was more holy. You were fulfilling this higher law by being a plural wife.

So, not just allowed. Required. By God.

MUSSER: Their measure of success is for the women to marry a good, faithful, priesthood man, where she brings forth as many children as she can. Because the more children he has, the — the larger of a kingdom he has.

Not exactly mainstream belief, or even legal, for that matter.

But, this is, after all, America, blessed with a constitution that quite pointedly shelters religious freedoms — in all their stunning variety.