Highland Warlord by Amy Jarecki

After the crowning of Robert the Bruce, Sir James Douglas is sent to the Scottish borders to wreak havoc on those loyal to Edward of England. But his plans go wildly astray when Lady Ailish Maxwell’s brother is captured by her traitorous uncle. James has every intention of finding the lad but when Her Ladyship announces she’s joining the quest, he’s not about to let her go, no matter how beautiful her crystal eyes, or convincing her silver tongue.

And Ailish will not sit idle while her brother, the true heir to the Maxwell dynasty, is taken deeper into the enemy’s lair. After putting forth every ounce of reasoning she can muster, Sir James agrees to allow her to pose as his wife. But what she doesn’t count on is falling in love with the braw Highlander. And as they ride farther into enemy lands, they cannot ignore the intensity of the passion simmering between them—though it could very well ruin everything they have worked so hard to preserve.