The Duke of Rockcliffe returns home to England from the British Army of Occupation which after the defeat of Napoleon in 1815 is located at Cambrai.
He had left England seven years ago when he was merely a young Lieutenant who intended to spend his life in the Army.
Owing to the death of several Heir Presumptives to the Dukedom, he finds himself unexpectedly and to his great surprise the new Duke.
He also discovers that he has a Ward called Nelita, the daughter of General Sir Edward Sheldon who had been his Commander. Sir Edward was killed by a stray cannon ball at the Battle of Waterloo.
General Sheldon made the Duke Nelita's Guardian because she has inherited her mother's enormous fortune and he was afraid of fortune-hunters.
The Duke first heard about the stunningly beautiful and lively Nelita when he read in The Morning Post a description of how, in answer to a challenge, she walked along the parapet of a house in Belgrave Square and was watched by a large crowd who were encouraging her.
He is determined that this sort of behaviour should not continue and he then finds that she has been staying with a fast member of Society called Lady Marshbanks, who is not considered to be a suitable chaperone for Nelita.
Her next escapade is to show him that she is not a dull and conventional debutante.
She dresses up, painted and disguised, as a Society beauty and is clever enough to deceive two of the Duke's friends who are dining with him.
He takes her to the Ascot races where they have luncheon with the Prince Regent and the Duke guesses that she has another prank in her mind that he is resolved to stop before it goes too far.
Nelita, however, finds that a particularly unpleasant fortune-hunter, Sir James Jensen, is trying to blackmail her best friend in London.
She manages to outwit Sir James, but he plans a terrible revenge for Nelita.
She is terrified at his dastardly plot and has no idea how she can escape from him.