Hi, I'm looking for the title and/or author of this historical romance novel published in the 80's or 90's.  The hero disguises as a dandy but at night he is a tall, dark and handsome man envolved in espionage.  The herione goes to him for help at the beginning of the novel and he falls for her, but she just sees him as a friend because of his clothes and the white wig he wears.  However, she hears about the exploits of his as himself and wants to help in the cause.  She delivers a message to him one night when the regular messanger cannot.  They have a sexual encounter at this point.  She must get married and she hopes that he will come to her rescue but he tells her he cannot.  He offers her marriage disguised as the dandy and she eventually accepts.  On their wedding night he reveals his true self.  He also owns a ship where he keeps in a cavern under his home and reaches it through a secret passage, which the heroine eventually finds and stows away on when he goes on one of his missions.
I hope somebody can help find this novel.