Laura Gaddy, who grew up as a devout Latter-day Saint in North Carolina, says she felt her surety in church principles begin to unravel in 2015, when leaders pulled Joseph Smith’s “seer stone” from a vault and showed it to the media. For her, according to court documents, the event signaled that the faith’s founding prophet had not translated the Book of Mormon, the church’s signature scripture, directly from gold plates inscribed with reformed Egyptian characters, but instead had dictated the narrative “from a stone with his head in a hat.” Gaddy came to be deeply troubled by what she...