A Gifted Earl by Arietta Richmond

Mr Morgan Follett, the son of a second son of an Earl, went into the military, because that is what was expected of him. He soon discovered that he was not suited to it, and so sought other opportunities. Years later, settled into a happy life far from society, he acts to help an injured girl. A girl he expects to never meet again.
Lady Venetia Chater is beautiful, and talented, but she is also rash and impetuous. When that rashness leads her to injury and possible death, it is only the assistance of a man whose name she doesn’t even know, which saves her – but she is left with a scar, nonetheless. She never expects to see the man again.