Barbara Cartland's A Duel of Hearts
Lady Caroline Faye meets Lord Vane Brecon; the attraction is instant. When she finds out that he is being accused of a murder he did not commit, she sets out to prove him innocent, and takes a position in his family castle as a companion to his mother. She discovers that the Brecon family is not only wealthy in land and fortune, but rich in secrets lurking behind the castle walls.