Stealth by Janie Crouch

In this classic tale, originally known as Infiltration, from USA TODAY bestselling author Janie Crouch, two people reunite when they're forced to worked undercover - and sparks still fly.

The wrong place at the wrong time — that's the only way Sophia Reardon could explain her predicament. She wasn't even an FBI field agent and now she was being taken hostage. By her ex-boyfriend Cameron Branson. The moment Sophia walked into his undercover opeartion, Cameron warned her that his “employers” would want to break her.

So keeping her by his side, pretending not to have feelings for her, was the best way to maintain his role in the dangerous organisation. And the only way to keep them both safe. Because if they got their hands on her, she could expose him and his secrets. And then they'd no longer have any reason to keep her around...