Pursuing The Traitor by Leighann Dobbs, Harmony Williams

When Lucy Graylocke intercepts a message meant for her spymaster brother regarding the dangerous French spy Monsieur V., she arranges a trip to London to catch the spy herself. After all, she may be the only person in England who could recognize him. But when her efforts to catch the enemy spy throw her in the path of the Marquess of Brackley, she gets more than she bargained for. The Marquess has a rakish reputation of the worst caliber and her brother has warned her away from Brackley many times. Naturally, that makes him all the more intriguing to Lucy. Could the handsome and mysterious Marquess be after the same thing she is?

Alexander Douglass, the Marquess of Brackley, will stop at nothing to capture Monsieur V., the spy who tore his family apart. But when Lucy Graylocke keeps getting in his way, he has to wonder what she’s after. She is, after all, the sister of one of the most influential spymasters in England. Alex knows Lucy’s brothers would never let her get involved in espionage so he fears Lucy doesn’t know what she is getting herself into. It’s up to Alex to make sure she doesn’t get hurt. Luckily, keeping an eye on the raven-haired beauty will not be a hardship.
But just when Lucy gets close to discovering the identity of the spy, a heart-wrenching disaster throws her world off kilter and Alex is forced to choose between the revenge he’s desperately sought for years and his love for Lucy.