Review from Goodreads:
Someone To Protect Her (Montana Confidential) (Harlequin Intrigue #629)
Ex-military man Frank Connelly vows to deliver scientist C.J. Birch safely to a research facility for some important undercover work. Plans go awry when a mercenary named Gilad forces down their plane in the wilds of Montana. They must find their way to civilization -- and stay alive. For Gilad is a man of many faces and very, very deadly.