Rome is ruled by an authoritarian government. Its chief of police Baron Scarpia suppresses all dissent. When Angelotti, an escaped political prisoner, seeks refuge in a church, he meets the artist Mario Cavaradossi, who agrees to help him.
Cavaradossi’s lover is Floria Tosca, one of Rome’s most adored singers. Baron Scarpia has long obsessed over her. Suspecting that Cavaradossi is linked to the escape of Angelotti, he sees an opportunity to pursue his desires for Tosca.
Cavaradossi is arrested. Tosca seeks out Baron Scarpia and begs him to let her lover go. In her desperation she reveals Angelotti’s whereabouts, but this implicates her lover in a capital crime.
Scarpia offers Tosca an ultimatum. He will spare her lover, but she must give herself to him. Tosca, seeing no other solution, agrees and the Baron sends a command to the firing squad to load their rifles with blanks. He then goes to embrace Tosca, but she grabs a knife and stabs him to death.
Tosca goes to Cavaradossi in his cell and tells him that he must play along with a mock-execution, after which they will be allowed to flee Rome. Cavaradossi is led away, the firing squad load their rifles, aim and fire. Cavaradossi’s body falls.
Tosca realises that Scarpia has betrayed her. Suddenly Scarpia’s men arrive, having discovered the Baron’s body. They rush to arrest Tosca, but she flees their grasp and leaps from a parapet to her death.