Dreams of Lilacs by Lynn Kurland

Isabelle de Piaget is determined to elude her overprotective family by means of a hasty escape to France. But instead of making a surprise visit to her brother there, she winds up shipwrecked on the French coast with no memory of who she is or how she came to awaken in the dark and forbidding castle of an equally brooding lord.
Gervase de Seger rescues—very reluctantly—the bedraggled urchin he finds on the road and puts her to work where he can ignore her. Unfortunately, he soon realizes that her brother is an intimidating lord who is going to be absolutely furious when he learns that his beloved sister has been laboring as a scullery maid. Yet Isabelle may be the one who holds the key to solving Gervase’s most pressing problem: that someone has been trying to finish the task of separating him from his title and his lands.

Finding the truth propels Gervase and Isabelle from the buried secrets of half-ruined keeps to the glittering French court, and to the realization that love can blossom in the most perilous circumstances—and in the most unexpected places of the heart . . .