Set in the Papal States in the first half of the 19th century, it tells the story of the Roman noblewoman Vanina Vanini and her secret love for the Carbonaro Pietro Mirilli. The latter, given his commitments in the underground struggle, decides to abandon his young lover, who is nevertheless willing to marry him. Left alone, Vanina is unable to escape her despair and tries in every way to reunite with her companion, even going so far as to denounce the Carbonari to the Cardinal of Romagna, naming them all except Pietro and revealing the hiding place where they meet. Pietro, learning of Vanina's betrayal, casts her out. Only then does Vanina realize the gravity of her actions and decides to join the Carbonari, even participating in combat operations, during one of which she is wounded. This brings the two young people closer together forever.