Eldorado by Baroness Orczy (Scarlet Pimpernel)

Armand St Just, his beautiful sister Marguerite and her husband Sir Percy Blakeney are once again caught up in the turmoil of revolutionary France. And adventurer Baron de Batz enters the story. It is 1794 and Paris, despite the horrors that had stained her walls, had remained a city of pleasure, with the knife of the guillotine dropping less frequently. But this could change ....