Twin of Fire by Jude Deveraux

Blair Chandler loved a man of challenge and passion: Dr. Lee Westfield. Still, she clung to her own dream of practicing medicine in Chandler, Colorado. With her impetuous spirit she had won her degree, and then won Lee’s heart.

Yet even as their ardor mounted, she was shunned by people who feared a lady doctor. And there were nights he would disappear, only to return exhausted, haunted. His silence imperiled their love. But the truth would surely imperil life.