Unexpected Clue by Elle James

Special Agent Ben Parrish had been thought dead for two months. So when he suddenly reappeared, bruised and battered on his pregnant wife's doorstep, claiming he'd been working deep undercover, even the FBI had trouble believing him. Before he could be debriefed, though, he had to convince Ava to trust him with her safety and that of their unborn baby. But with his captors hot on his trail, Ben had little time to explain to Ava how much he'd missed her. Now, even as they barely stayed one step ahead of the danger and protecting Ava became his top priority, Ben had never felt happier to be home....