The Tangled Web — Anne Benson

Amanda Winthrop fears for her reputation when she is thrust into the carriage of the infinitely desirable Charles Latimer. But when the carriage overturns and a blow on the head plunges Charles into total amnesia, Amanda sees a way to turn the accident to her own advantage. She will convince Charles that he is her long-lost brother and reunite him with her ailing grandfather. But soon Amanda, now hopelessly enamored of Charles, will worry that perhaps the eligible man's memory might never return.