Bad Boys Undercover series by Helenkay Dimon

Playing Dirty (#1): As an elite Alliance agent—the joint undercover operation of MI6, the British Secret Intelligence Service, and the CIA—Ford Decker lives for the adrenaline. But when he befriends sexy property manager Shay Alexander in hopes of finding her cousin, a known national security threat, Ford crosses the line, getting to know her better… in bed. After being burned by her last relationship, Shay wants to take things slow. Yet she can’t keep her hands off the drop-dead gorgeous hottie who’s moved into her apartment building. So when Ford’s identity as an undercover agent is exposed, his betrayal cuts deep. Shay never wants to see him again, but Ford can’t let her go, not when her life is still in danger. He will sacrifice everything to protect her, then be prepared to walk away from the only woman he’s ever loved, even if it breaks him.

Falling Hard (#2): After a grueling assignment with the black ops force known as the Alliance, Weston Brown is craving downtime. Instead, he’s pulled into his deadliest operation, in the one place he never wanted to see again. No-nonsense and so damn hot, Lexi Turner lied to get him to her mountain clinic in Pakistan. But the threat is terrifyingly real. Lexi has been asking too many questions, drawing the wrong kind of attention. As soon as she lays eyes on West, she can tell he’s quiet—yet tough—and has a rescue complex which will come in handy for going up against the world’s most ruthless gunrunners. Cut off from the rest of the Alliance, Lexi and West navigate the brutal terrain and a primal sexual attraction. Sticking around has never been West’s way, but now he’ll use every resource to keep Lexi by his side, safe from a killer who leaves no loose ends behind.