By order of the Minister of Foreign Affairs, Châtelet Police Commissioner Nicolas Le Floc sets out on a life-threatening journey from Paris to Vienna to expose the enemy's spy network, which may even involve the resident of French intelligence, Abbé Georgel. At the same time, he must provide a report on the recent expansion of the borders of the empire up to Moldavia, as well as on the number and nature of the troops stationed there. It is there that he will learn who became the organizer of the so-called flour riots in France.