Bird in Hand by Allison Lane
A daring young lord, seeing a young woman floundering in an icy river, immediately dives to her rescue. But in saving her life, he almost loses his own! When he comes to, he finds himself alone with the mysterious lady in a small country cottage. And though he had successfully avoided the marriage-minded maidens of the "ton" for years, he felt honor-bound to propose to his beautiful benefactor. After all, they had spent the night alone, and the scandal would be unbearable. But the woman vehemently refuses, and disappears. But the young lord finds himself not so willing to let go of her, and the chase is on.