One of a Kind - Singular Sensation, #7.5

He's made a name for himself with his fists, but will he fight for her? For far too many years, Hugh Tetford-Earl of Hazelton-has enjoyed his bachelorhood by surrounding himself with fellow club members from the Rogue's Arcade and prowling London with those brothers-in-arms. As he continues to ignore the responsibilities to his title in favor of indulging in illegal boxing in his leisure time, a valuable piece of jewelry with ties to his past suddenly comes into his possession and leads to him being beaten bloody. Miss Annabelle Harding-sister to Lord Timelbury-has never understood the arbitrary and snobbish rules of beau monde society.
More comfortable playing the hoyden and living as a headstrong miss, she's done as she's pleased while in the country, but now that she's in London, it's difficult to fit in, until one evening when she finds an unconscious, bleeding man left for dead in Hyde Park, which is when she truly discovers her purpose. As it becomes apparent the earl has lost his memory, Annabelle does all she can to help him restore them, especially since there's a spark of desire between them.
He's forgotten how to box, so his fellow club members rally around in order to give him fisticuff lessons. In the course of retracing his life through London, the two develop feelings for each other but when a man intent on taking back a moonstone necklace threatens them both, Hugh will need to dig deep in order to fight for everything he now holds dear.