The Illegitimate Duke by Sophie Barnes

United in a common cause… Juliette Matthews longs to be much more than just another pretty ornament in society. But using her recently acquired fortune to do some good is more complicated than she anticipated. Young ladies are not expected to risk their safety in helping the less fortunate. And the one gentleman who could help in her mission is stubborn, infernally handsome—and far too honorable to act on their mutual attraction.

And in a desire impossible to deny… Florian Lowell has suddenly been made heir to the Duke of Redding—a far cry from his status as a dedicated physician. Yet even with his new role as the country’s most eligible bachelor, the beautiful, fearless Juliette is utterly beyond his reach. The scandalous circumstances of his birth would destroy both their reputations if they became known. But when a more urgent danger threatens Juliette’s life, Florian must gamble everything…including the heart only one woman can tame.