''Senso'' is set in Italy around 1866, the year the Third Italian War of Independence would see the Veneto and most of Friuli-Venezia Giulia united to Italy after the Seven Weeks' War between Austrian Empire on one side and Prussia and Italy on the other. The story opens in the La Fenice opera house in Venice during a performance of ''Il Trovatore''. At the close of Il trovatore#Roles's rousing aria ''Di quella pira'', the opera is interrupted by a boisterous protest by Italian Nationalists against the occupying Austrian troops present in the theater. Livia Serpieri, an Italian countess, unhappily married to a stuffy older aristocrat, bears witness to this and tries to conceal the fact that her cousin Marquis Roberto Ussoni has organized the protest. During the commotion, she meets a dashing young Austrian Officer named Franz Mahler, and is instantly smitten with him. The two begin a secret love affair. Despite the fact that Franz was responsible for sending Roberto into exile for his radical behavior, Livia vainly pretends not to be aware of it.