Henri Ambergnac has become Count of the estate from which his name was originally taken, and fifteen years have passed since his return to France from America, years that saw the rise to prominence of Napoleon Bonaparte. Amongst those whose best interests are to be had serving the new régime is a man working covertly for the Minister of Police, and when he uncovers a plot to overthrow the Emperor he recognises a rare opportunity for advancement. Agent Caustique also discovers that Ambergnac has given a home to two English prisoners of the state; furthermore he has set in motion a scheme to help their relation escape from the notorious Bitche prison. This gives Caustique another chance for promotion and at the same time revenge himself on a member of the old aristocracy, that class of person he has been intent on destroying for over twenty years.