Talia's the Villain #1: She's not actually the villain, but all of their problems stem from her. So it all begins when her partner, Kris, who she's on the internship with makes a comment about the circulating rumors that she's abusing her gift of empathy. Now, to most normal folks, well, that sucks. Might get a little bummed, somewhat annoyed, but to Talia, the special one, she takes a simple rumor and her "empathy" gift torpedoes it into a large scale problem. All because she didn't talk about it to anyone. Since empathy is supposed to be how you relate to others and not about your own feelings of inadequacy, I'm not quite sure how this makes sense.
Talia's the Villain #2: So, the entire middle half of the book takes place in a Waystation, as they're snowed in. Their problems are the blizzard outside, but mostly Talia, inside. Because she might EMOTION them all to death. Man, I wish I was joking. But that's the gigantic threat. That she'll project her empathy on Kris and since that's so super dangerous, they've gotta get it under control. So they spend the majority of the time banging as friends (although they've stated they feel brotherly and sisterly towards one another which creeps me out, because a casual fuck does not normally happen between brothers and sisters) and working on fixing her out of control gift.
Talia's the Villain #3: So, after Talia's under control, they continue on their path, solving problems as Heralds are apt to do. They encounter a rapist in a village and Talia uses her mind juju on him to trap him in a loop of torture. Magically, everything's better and even though she never really established the moral implications of her gift, she pretty much decides she doesn't give a damn by the end, making the entire struggle through the book a pointless obsolete.