Like the Englishmen who faced down the French army, the men who love Marielle Petersham, Duchess of Stonegreave, usually die. Hence, the ton has dubbed her the French Duchess. After a particularly notorious indiscretion, Marielle retired from society, determined to immerse herself in good works to wash the stain from her family name for the next generations.

Captain Sir Richard Campion despises his childhood friend for the mess she made of her life, especially since it led to his best friend's death. But now Richard has been tasked by the Crown to stop a plot to assassinate Napoleon Bonaparte that could plunge Europe back into war. Marielle is the one person who holds a clue to the plotters, and so he must seek her out and discover where her loyalties lie, even if it involves a bit of subterfuge. As they dash through France, determined to head off disaster, old affections begin to reignite. But can they truly trust one another long enough to save the continent?