One Wicked Sin by Nicola Cornick
Once the toast of the ton, Lottie Cummings is now notorious for being divorced. Shunned by society, the destitute beauty is lured to become a Covent Garden courtesan. Until a dangerous rake saves her with a scandalous offer.
The illegitimate son of a duke, Ethan Ryder rose to the ranks of Napoleon's most trusted cavalry officer--until his capture landed him in England as a prisoner of war. Now on parole, Ethan is planning his most audacious coup yet. But he needs Lottie's help to create a spectacular diversion. Yet their pact ignites a passionate bond that may scandalize even these two wicked souls....