The Highlander's Charm. The Stolen Bride Series, #8

They should be enemies. But passion and love know no bounds. Returning from battle to England, Samuel de Mowbray discovers that his two younger sisters have been stolen by Highlanders. Determined to save them from vicious warriors, he convinces the king to send him north. While there, he discovers that his loyalties are wavering and that a headstrong, feisty lass could destroy everything he believes. Catriona Buchanan must travel north to ask for help in saving her brother and ridding her castle of brutal English knights.
Unfortunately, to do so, she must trust in the thing she mistrusts the most-an Englishman. Minute by minute, the man who should be her enemy breaks down her defenses. There is something different about him and she can't help but be captivated by Samuel, and his steamy kisses.