The Betrothed

The action takes place in the Welsh Marches during the latter part of the reign of Henry II, after 1187. Eveline, the 16-year-old daughter of Sir Raymond Berenger, is rescued from a Welsh siege by the forces of Damian Lacy. She is betrothed to his uncle Sir Hugo, who leaves on a crusade. Rebels led by Ranald Lacy attempt to kidnap her, and Damian fights them off, but a confused sequence of events convinces the King that she and her beloved are in league against him.

Reference: http://en.wikipedia.org/wiki/The_Betrothed_(1825_novel)