Between Love and Honor - Men of the Secret Service, #3

The Secret Service's number one cyber asset, Special Agent Ben Segar, has a reputation for playing it straight... until a top-secret assignment has him cozying up to his runaway prom-date. Now, he's willing to break a few rules to get even. Potentially unmasking a traitor at the same time makes his revenge even sweeter. Photographer Quinn Darby was born into the spy game. When her very existence is threatened, she turns to the man she vowed never to deceive again for help.
Except Ben is no longer the mild-mannered lab partner she once loved. Instead, he's a full-grown, Alpha-man whose appeal is nearly irresistible. And to protect him, she must keep him from learning the truth about her double life. Soon, Quinn and Ben are embroiled in a cat-and-mouse game with the enemy-and each other. Ben finds himself risking his job, national security and his life for a woman he swore to never trust again.
As the case intensifies, so does the heat between them, until the op's greatest casualties may be their hearts.