Two anonymous letters :the title is symbolic.The fascist years mean informers,cowardice.But there were resistant fighters too,and the movie 's purpose is to show the two sides,through a woman's fate (the great actress of the era Clara Calamai,famous for the second -the first one was French- and IMHO best version of "the postman always rings twice " ,"ossessione") .This woman ditches her fiancé ,a soldier coming back from war ,and lives with Tullio ,a collaborationist .The movie tells the woman's redemption;once a selfish bitch,we see her rebel against her lover's despicable attitude ,till she finally becomes an heroine by saving the whole network.The movie ,one of the two first Italian works given over to resistance (along with Rossellini's "Roma Cita Aperta") ends on an optimistic note,which people did need just after all those dark hours.