Dawn by Erin M. Leaf

Saige Ellis can spot a liar from a hundred yards away, and she knows her history professor is bad news. She hates the way he hides behind his stupid sunglasses and beard. She hates the way his ridiculously perfect body makes her feel. When he asks her to stay after class, she asks him what he’s trying to prove.

Isaac Dawn hates having to hide his identity, but it’s the only way he can get close to Saige without tipping everyone off about his identity as a Sentry. He knows she’s his perfect match, but she’s skittish and angry, and for good reason—her abusive father has been stalking her for years. When he asks her to give him a chance, Saige demands the truth, and he blows it.

However, when murderous aliens are real, and a mysterious shadow follows Saige home, is her demand for honesty worth her life? Can she accept Isaac’s help without losing herself?