Bodyguard by Melanie Shawn

Savannah:
Twelve years ago, when I was sixteen, everything I loved was ripped away from me in an instant when my father and I were taken into WITSEC. My home. My friends. My life. And Gage Crawford, the only boy I’d ever loved.
But two days ago, the men that we’d been hiding from found us. They killed my father, and I barely escaped. They’re after me, and I don’t know how to outrun them.
Except…that boy I lost when I was sixteen has grown into a man, and he might be the only hope I have of survival.

Gage:
My heart was ripped apart the night Savannah Langley disappeared. I dropped her off at home on the night of her sixteenth birthday, and never saw her again. I didn’t know if she was dead or alive. And I hadn’t been there to protect her.
I swore that I would never let another person down again the way I’d clearly failed her. That anyone else who ever needed my protection would get it.
When Savannah shows up on my porch in the middle of the night twelve years later, I’m stunned. And when she looks up at me and asks me to help her because I’m the only one who can save her life, I know I don’t have a choice. I am going to save her. Or I am going to die trying.