Bel Demonio takes place in the Spoleto region of Italy between 1625 and 1655. Ercole Vitelli murders his cousin, Francis Vitelli, who is the legitimate heir of the wealthy Monteleone family, under the eyes of Francis' son, Andrea. Fifteen years later, Andrea returns seeking revenge, posing as "Demonio," the leader of a ring of bandits. Bel Demonio (1850) and The Companions of the Silence (1857), were retroactively linked by Paul Féval to his saga of the Black Coats, functioning as the backstory of that vast criminal conspiracy. Andrea Vitelli is cast in the same mold as Monte-Cristo. At the heart of the plot is revenge for a crime committed with impunity. But if the revenge plot is the engine that keeps the action going, Féval can't hide his fascination for the character of the criminal mastermind at the center of it all, even if at heart he is secretly a hero.
Bel Demonio is an important stepping-stone in the development of modern popular fiction.