When Katie answers the call of duty, she awakens the call of her heart.

Katie Russell loves working as a telephone operator in Mercy Falls, California. But since childhood she has been expected to marry well. Her family presses for an engagement to wealthy bachelor Bartholomew Foster and though he doesn't stir her heart, their engagement promises a secure financial future.

Working the phone lines one evening, Katie overhears a chilling exchange between her friend Eliza and a familiar male voice. Katie soon learns that Eliza has disappeared, and the crime may be linked to another investigation by handsome new lighthouse keeper, Will Jesperson. Katie and Will soon form an alliance. An alliance that slowly blossoms into something more.

Despite the danger surrounding her, Katie is powerfully drawn to Will. But she is not at liberty to marry for love. And though society forbids their growing affection, Katie can't help but notice Will's sense of peace. It's a peace that rests on his trust in God—a trust that Katie has never had to depend on, with her future so clearly mapped out before her.

But the more Katie uncovers of the mystery, the more she discovers about herself, her past, and the brilliant future that could be hers if only she has the courage to trust in God and follow where her heart so fearlessly leads.