“I MAKE A LOT OF MONEY AS A CALL GIRL” wasn't the answer author Steve Cuno expected when he asked a new acquaintance how she planned to capitalize her start-up business.

Wait, hold on, he thought. In Salt Lake City? Home to The Church of Jesus Christ of Latter-day Saints, the Mormon Church, where all it takes to become the object of steamy gossip is for a neighbor to see you take a sip of coffee? In a religion where nonmarital sex is second in seriousness to murder?

“You've no idea the people I could get in trouble,” she told him. She'd entertained politicians, police officers, judges, defense lawyers, prosecutors, doctors—all of them married, almost all of them practicing Mormons. Many were highly visible, highly regarded leaders in the faith.

So began Cuno's behind-the-scenes investigation into Salt Lake City's prostitution industry. Over the course of three years, he interviewed prostitutes, johns, police officers, social workers, and massage-parlor owners—and uncovered a surprising underside to the Mormon Church's carefully cultivated image of wholesomeness and family values. He found that Salt Lake's prostitutes—“sex workers” or “providers,” as they prefer to be known—don't live in the illusory experience they create for their clients. Many are multilingual and hold college degrees. They fix meals, drive kids to school, help with homework, handle household chores, socialize with others in the community, have love lives of their own—and, yes, go to church, sometimes with the very people who sneak out to meet them.

With wit and sensitivity, Behind the Mormon Curtain takes a deep dive into the quintessential American religion and the world's oldest profession, as Cuno tells the story of what he discovered, how he discovered it, and what it reveals not just about Mormons, but about us all.