Kiss Me While I Sleep by Linda Howard

If you sense someone’s watching you from afar, or if you feel a shadow other than your own at your back, I might as well pack it up and call it a day. It’s a job that makes a killing. Efficient, professional, and without apology, Lily Mansfield is a hired assassin, working as a contract agent for the CIA. Her targets are the powerful and corrupt, those who can’t be touched by the law. Now, after nineteen years of service, Lily has been drawn into a dangerous game that hasn’t been sanctioned, seeking vengeance for her own reasons. Each move bolder than the next, she is compromising her superiors, drawing unwanted attention, and endangering her very life. Though stress and shock have made her feel somewhat invincible and a little cocky, Lily knows that she too can be taken out in an instant. And if it’s her time, so be it. She intends to go down fighting. A CIA agent himself, Lucas Swain recognizes the signs of trauma in the line of fire. His orders: either bring her in or bring her down