In 1848, Hornblower, now an Admiral of the Fleet, is enjoying a well-earned retirement on his country estate in Kent when, late one stormy night, a seeming madman claiming to be Napoleon, arrives at his front door and requests his help. The Frenchman has been travelling by train to Dover, but a landslide has delayed the train and he is seeking assistance to complete his journey. Hornblower's wife Barbara is favourably impressed with the man's manners and persuades her husband to provide his carriage to oblige the visitor, although Hornblower remains privately convinced that the Frenchman is a lunatic.
A month later, the Hornblowers find that their caller really was Napoleon—Napoleon III of France, nephew of Napoleon I—and that he was on his way to Paris to contest the office of President of France. After winning the election, he confers on Hornblower the insignia of a Chevalier of the Legion of Honour and gives a sapphire to his wife, in gratitude for their timely assistance.