A mysterious prisoner dies while trying to escape from the prison of Fort-Lévêque. Nicolas le Floch's investigation on the murder of the stranger will lead him right in the middle of an espionage case involving the Minister of the Navy, Monsieur de Sartine, who will stop at nothing to establish the supremacy of the French fleet in the war against the English.

A mysterious prisoner dies while trying to escape from the prison of Fort-Lévêque. Nicolas le Floch's investigation on the murder of the stranger will lead him right in the middle of an espionage case involving the Minister of the Navy, Monsieur de Sartine, who will stop at nothing to establish the supremacy of the French fleet in the war against the English.