A typical Mormon family: two parents, two kids. Mother and father love each other deeply. Enough that they've committed to stay together for eternity. A son on the brink of priesthood initiation. A daughter preparing for official membership; a covenant decision.

Like any typical family anywhere, trouble brews beneath the surface. The marriage strains at the ties that bind. The boy quails beneath a looming threat. The girl despairs that she will ever qualify.

Still, the beliefs they tangle with each day of their lives-individually, and as a unit-may offer them just enough direction to...