Thin Ice by Maryann Jordan

Logan (Preacher) Bishop, retired Navy SEAL, flew tourists on helicopter rides over the mountains of Montana and occasionally rescued skiers from snowy slopes. With the threat of terrorists developing means of biological warfare, he jumped at the chance to run a mission in Alaska, monitoring the activities of a newly established ISIS cell.
Vivian Sanders, a biologist with the Department of Homeland Security, was tasked with finding out what the terrorists were creating. Assigned to work with an agent on a cell in Alaska, she was stunned to find she was being paired with a security specialist and he knew nothing about their cover—living next door to the terrorists and pretending to be married.
Precise in his planning and executions of missions, the impulsive Viv drove Logan to distraction and of all his missions, he was certain this one would fail. Learning to work together, Logan and Viv discover opposites do attract. But the secret Logan carries—how he is to finish the mission—is one he is afraid she won’t be able to accept.
When the chemicals created by the terrorists next door threatened to be tested on a small town in Alaska, they fight to survive…both hoping their love survives the battle as well.