The Duchess and the Spy — Marly Mathews

Isabella De Clermont is alone in the world. A witch with formidable gifts, she comes across the British Spy known as the Wolf while a captive in France. Seeking to have Napoleon Bonaparte restore her lands, in France, and the title of the Duchess of St. Malo to her, she awaits the day that she can escape the man who took her from all that she knew and loved.
Christopher Brandon, the Marquess of Wyndham is the Wolf. Realizing that Isabella has been enlisted by Napoleon to spy for them when she returns to England, he knows he must keep an eye on her, and as their passionate personalities collide, marriage seems the only respectable option for them both.
But danger chases Isabella, and Christopher must be her Saint Christopher… the only man that can save her from her Fate.