Dark Future — K.C. Klein

A woman caught between two futures...
Awakened in the middle of the night by a future version of herself, Kris Davenport is given a mission: go travel in time to save the world--and his life. Of course, her future self doesn't tell her who he is, just sends her into the darkness and straight into an alien invasion.

Must choose between the man who has her heart...
He turns out to be ConRad Smith, the callous, untrusting military commander of Earth's army and the world's last defense against evil. There's only one way for Smith to know for sure if this strange woman is an alien spy--slice her throat. Except, he didn't anticipate the desire he would feel as he interrogates the hot-tempered, warm-blooded woman.

Or the fate that saves the world...
As Kris and ConRad struggle to trust each other in a world on the brink of destruction, they each will have to face the ultimate choice of whether to fight or die... survive or forgive.