The Counterfeit Mistress(Fairbourne Quartet‪)‬

The beauty. The spy. And the beholder.
From the beloved New York Times bestselling Madeline Hunter comes this riveting historical romance, in which a darkly handsome nobleman is determined to unmask a delicate and mysterious young beauty . . .
A refugee from the war in France, Marielle Lyon has established herself at the fringes of London society. Claiming to be the niece of an executed aristocrat, Marielle welcomes the gossip that she is a spy. The more eyes she has watching her, the better protected she is-and the better chance she has of saving her father's life.

A warrior at heart, Alban Norwood, Viscount Kendale, would still be in uniform if not for his older brother's untimely death. After all he's seen, Kendale doesn't trust the French-or their femmes fatales. He has set up a surveillance network to ferret out undercover agents, and he believes he's found one in the delicate, mysterious Marielle.

Ready to pounce on his tempting prey, Kendale arranges a meeting with Marielle, who is more beautiful and more cunning than he anticipated. But the Viscount is ready to do whatever it takes to unmask her-even if it means playing a game of seduction . . .