Absolutely the duchess. Why was she kidnapped, though? Was the idiot count actually so insane he would have had a marquis's daughter kidnapped to be used as a plaything by her daughter? That would be absolutely bonkers. I suppose it would be more likely that random professional kidnappers took her, with the intention of simply selling her for good money to anyone. It would have been just a coincidence she ended up in count Darrington's household.