Sealed: An Unexpected Journey into the Heart of Grace

Katie Langston is an unlikely convert to Christianity.

She grew up in a devout, conservative Mormon family in Utah, served a proselytizing mission to Bulgaria when she was 21, married for "time and all eternity" in the Mormon temple when she was 23. From the outside, she had a typical Mormon life. Inside, she was coming apart at the seams.

From childhood, she battled "The Questions"-obsessive-compulsive disorder, though she didn't have a diagnosis for it until much later-and lived inside a co...