Shroud of Fog — Willo Davis Roberts

Hannah Starn had been the most vindictive old woman the town had known, and then, in the fog and darkness, she was dead--fallen from the tower window. Although Amy didn't grieve for her, she was desperate to know who had hated her guardian that much. Had it been one of the other two orphan girls Hannah had raised and tormented--or their husbands? Everyone had a motive, including Amy. But who had taken the final step.
Amy had to know, for all the clues pointed to the man she loved. She had to uncover the secret behind the violent deaths, for she had a life to win--or to lose.