If You Give a Rake a Ruby (Jewels of the Ton, #2)

Fallon, the Marchioness of Mystery, is a celebrated courtesan with a mysterious past. Warrick Fitzhugh will do anything to protect his compatriots in the Foreign Office, including seduce Fallon, who he thinks can lead him to the deadliest crime lord in London. Fallon is not who Warrick thinks she is, but her secrets answer his desire.