She's a single mom with a secret. He's a former Delta who doesn't let people too close. Aria Callas understands struggle and sacrifice. Getting pregnant at sixteen, she's spent more than a decade and a half ensuring her and her son's safety the only way she knows how-by staying on the move. Too long in one place and Zac's father bursts back into their lives, bringing nothing but chaos and pain in his wake. During those same sixteen years, Cole Turner's career as a Delta has taught him just how ugly and unforgiving the world can be. Now retired from the military and running a boxing club, Mercy Ring, with his ex-teammates, life is simple-until he notices the woman living across the street. He vowed years ago to never entrust his heart to another...but he can't get his enigmatic neighbor out of his head. When familiar danger inevitably finds Aria, Cole can't keep his distance any longer. He'll do whatever it takes to save her, even if that means putting his life-and his heart-on the line once more.