The Highlander’s Enigmatic Bride by Lydia Kendall

When Isabel Brown, the famous Duke of Gordon’s only daughter, loses her beloved brother in an ambush set up by the notorious clan Maccallion, the course of her entire life changes brutally.
Setting out on the riskiest journey for the sole purpose of seeking revenge for her brother’s death, she gets imprisoned by the fearsome but exquisitely handsome Laird of clan Maccallion.
Edan Maccallion, unaware of his captive’s mysterious identity, falls under the spell of her breathtaking beauty, never predicting that the price of his infatuation will be too high.
As Isabel’s adventure in captivity reveals the true culprit, everyone’s fates end up hanging by a thread, risking not only immediate peril but a bloody war.