I am a Shadow

Two generations have passed since the Kalvunais invaded the humans' frontier, but the question still remains: did they invade, or were they taken?
Novalie Gage is on the brink of her eighteenth birthday—and the day that she'll decide her profession. She knows she wants to be a Catcher—a person who dedicates their life to finding and prosecuting offending Kalvunais—but the job is dangerous, the training is hard and her would-be partner, Asher Endicott, is a little too fond of the aliens they're meant to hunt.
Asher tells her that the Kalvunais were not hostile in their coming, but were forced to flee to Earth when their own planet was destroyed. He also speaks of legends, myths that Novalie has grown up with but he claims are in fact true. He says there are those among them—the product of inter-species mating between the humans and Kalvunais—that have an unprecedented ability to control the elements. And what's more, he implies, Novalie may be one of them.