After her parents’ divorce, 16 year old Riley Grishin is forced to move from Portland, Oregon all the way to Little Brook, Maine, a small town that serves as the headquarters for Titan Technologies, an international science corporation. Having no friends, Riley spends most of her days running through the woods with her dog Tigger, and eavesdropping on her classmates—in particular, the gorgeous, but very strange, Aspen Montehugh. On the night of the homecoming game, Riley wakes up to find that her town is on fire, and being terrorized by an unseen monster. With the flames rapidly spreading, Riley and her dog Tigger have no choice but to pile up in their beat-up pickup truck and flee the town. But as they're driving away, they come across the only other survivor: Aspen. When Aspen and Riley reach safety, they realize that something far more strange and sinister is happening. According to the news, all of the other Titan Tech laboratories on the East Coast have spontaneously combusted. All air travel has been grounded, so Riley has no way to fly to her dad who lives in Seattle. Riley and her dad agree to meet up in Minneapolis, and Aspen comes along in hopes of finding her aunt. As they travel across the country, they are attacked by monsters and strange armed men in the dead of night. Slowly, Riley realizes that something's not quite right with Aspen, which puts her feelings for her—and her own humanity—to the ultimate test.