Fall from Grace by Jill Barnett

The Clan McNish has been raided and left starving by their bitter rivals, the McNabs. As granddaughter to the clan chieftain, Grace McNish decides it is her duty to capture and ransom a vile McNab. But she and her clan of misfits mistakenly capture the wrong man, Colin Campbell, Earl of Argyll and Lord of the Isles, who is on his way to decide the fate of the two warring clans.