Mirage by Regan Black

Forced to the fringes, he’s been content to thrive in shadows…
Years as a human guinea pig for the Unknown Identities program transformed Ben, body and mind, into the operative known as Chameleon. But one betrayal too many fractured his loyalty and now he’s determined to end the program, along with the man profiting from the destruction of good men and women.
…Until he sees her.
Mirage has no memory of her past, only what she has become under the brutal care of the covert operation: spy, killer, obedient operative with skills and stamina military leaders covet. Under orders to use her unique skills to locate and trap Chameleon, she becomes fascinated by the rogue operative’s ingenuity and insight. Though she doesn’t want a bodyguard, she definitely needs a way out.
When Ben promises answers and a secure future on her terms, Mirage takes a blind leap, hopeful that she and Ben can survive long enough to find true freedom and the redemption only love can bring.