ACT 1

The church of Sant'Andrea della Valle, noon Angelotti (a political dissident) having escaped from the prison of the Castel Sant'Angelo, hides in the family chapel. The painter, Mario Cavaradossi, is working in the church and when he recognizes Angelotti, he promises to help him. They are interrupted by the arrival of Floria Tosca, a famous opera singer and the lover of Cavaradossi. She is jealous by nature and furious when she discovers that Cavaradossi's painting of the Magdalene is a portrait of another woman. Cavaradossi placates her - they have agreed to a lovers' rendezvous that evening - and finally gets her to leave. He offers Angelotti a secure hiding place in his villa. A cannon shot announces that the escape has been discovered, so Cavaradossi and Angelotti leave hurriedly. A sacristan brings news of the defeat of the rebel forces, but the general excitement is cut short by the appearance of Baron Scarpia, the sadistic government enforcer, on the trail of Angelotti. Various cluses raise Scarpia's suspicions of the painter's part in Angelotti's escape. When Tosca returns to tll her lover that they cannot meet later because she is singing in a victory cantata for the Queen, Scarpia inflames her jealousy, suggesting that Cavaradossi is having an affair with another woman. As she rushes off to confront Cavaradossi, Scarpia orders his agents to follow her. The Te Deum of thanksgiving begins.

ACT 2

The Palazzo Farnese, later that evening Scarpia broods on his plans to entrap Cavaradossi and Angelotti and to have Tosca for himself. Spoletta, Scarpia's henchman, reports that Angelotti was not found at the villa but that he has arrested Cavaradossi. Cavaradossi denies any knowledge of Angelotti and is taken away for further "interrogation." Scarpia himself questions Tosca and uses Cavaradossi's screams to torture her, forcing her to reveal the hiding place. Cavaradossi savagely berates her for her betrayal. When Sciarrone, another aide to Scarpia, bursts in with the news that the announcement of victory was premature and that the rebels have won, Scarpia orders Cavaradossi's immediate execution. Tosca begs for her lover's life and Scarpia names his price: she must give herself to hm. Desperate, as she sees no alternative to save her lover, she agrees to Scarpia's bargain. Spoletta is seemingly ordered to perform a mock execution. As a safety, Tosca demands a safe-conduct document. Scarpia writes it and then turns to her to collect his reward.

ACT 3

The Castel Sant'Angelo, the next day, an hour before dawn Cavaradossi awaits his execution. As he writes a heartfelt farewell letter to Tosca, she appears. She confesses what she has done, and shows him the safe-conduct that will set them free. She explains the mock execution and how he must die convincingly. The firing squad enters and completes their task. When Tosca goes to Cavaradossi to compliment him on his acting, she discovers to her horror that the execution was all too real. Soldiers rush in, accusing her of Scarpia's murder, and she jumps to her death, denouncing him.