Danger at the Border (Northern Border Patrol Book 1)

UNSAFE TERRITORY 

When a mysterious toxin threatens lives and livelihoods near the border between the U.S. and Canada, Dr. Tessa Cleary is called to trace the source. But when the no-nonsense doctor is forced to work with border patrol agent Jeff Steele, she finds the lone wolf's dedication to his job—and country—chipping away at the walls around her heart. Just as Tessa and Jeff are about to uncover the toxin's deadly source, armed thugs kidnap them in the forest. Now they must trust each other to survive before time runs out for everyone. 

Northern Border Patrol: Keeping the U.S.–Canadian border safe