Unmasking the Earl by Elizabeth Keysian

Devastated by the disappearance of his sister, the Earl of Stranraer has gone to extraordinary lengths to find the notorious rake responsible, and enters his household incognito to wreak his vengeance. But his enemy has an unexpected protector—the innocent but headstrong Miss Cassandra Blythe.

Cassie is determined to learn the art of seduction. But she is blindsided by her body’s thrilling response to the wrong man—a mysterious servant who shows up at the most inauspicious moments to spoil her lessons in love with warnings of her imminent ruin. When she learns the handsome servant’s identity and the reason for his deception, she resolves to help Stranraer, but only if he abandons his vow to destroy his enemy.

The earl is sorely tempted to give the meddlesome beauty a lesson in seduction she’ll never forget. But she turns the tables, and he gets his own lesson in forgiveness…and love.