We've been walking for over three hours, and we haven't found a thing. Emily's stumbled and almost fell four times. I don't know if she's tired, scared, or so lost in her thoughts she's not paying attention. Either way, I don't allow myself to get farther than an arm's length from her, afraid if I do, she'll end up seriously hurting herself.

"Okay," Tom announces and stops. "Let's take a quick break."

"Finally," Emily mumbles.

I drop my backpack to the ...