Midnight Honor by Marsha Canham

She knew him by many names: Husband, Lover, Traitor.

Powerful, brave, irresistibly seductive, Angus Moy, Chief of Clan Chattan was everything Lady Anne could desire in a husband and lover. But that was before the winds of war tore through the Highlands dividing the loyalties of fathers and sons, brothers, and clans. While Angus was pledged to fight on the side of the English, Lady Anne is fiercely loyal to the Jacobite cause and leads her clansmen into battle.
Angus knows only too well the price of war, and as they face each other across the battlefield, his wife and clansmen are unaware of the dangerous secret that forced Angus to play the traitor—a secret he was bound to keep from Anne at all costs.

As the tides of war turn at Culloden, Anne is captured and Angus has one last chance to rescue her. One last chance to redeem himself in the eyes of the woman he had vowed to honor and protect forever.