How do you know God is real? In the emotionally-charged, fire-filled faith in which Addie Zierman grew up, the answer to this question was simple: Because you've FELT him. Now, at age 30, she feels nothing. Just the darkness pressing in. Just the winter cold. Just a buzzing silence where God's voice used to be. So she loads her two small children into the minivan one February afternoon and heads south in one last-ditch effort to find the Light. In...