Act I

Political fugitive Cesare Angelotti, a former Consul of the Roman Republic, is hiding in Sant'Andrea della Valle basilica, having escaped from prison. His sister, the Marchesa Attavanti, has prepared women’s clothes for him so that he can leave Rome unrecognised.

The Sacristan appears. He is unhappy with his job and with Mario Cavaradossi, the artist who is painting the church. The artist himself enters. The Sacristan recognises a beautiful parishioner in the painted image of Mary Magdalene, and Cavaradossi reflects on how different beauty can be. Grumbling, the Sacristan leaves, and Angelotti draws Cavaradossi’s attention. The artist is ready to help the fugitive, but Floria Tosca, a famous singer, comes in at this moment, and Angelotti hides again, taking Cavaradossi’s lunch basket with him.

Tosca has come to agree with her beloved Mario on their meeting in the evening. The whisper that she hears makes her suspicious and jealous. Cavaradossi manages to calm his lover. They agree to meet in the evening, after Tosca’s performance, and spend the night on his distant villa. Tosca is ready to leave when she recognises the Marchesa Attavanti in the painted image of Mary Magdalene. Her jealousy flares up once again, but Cavaradossi’s love wins and Tosca leaves appeased.

Angelotti reveals that his sister hid some women’s clothes for him in the chapel and that in the evening he is going to put on the disguise and leave the church. Cavaradossi offers to give him refuge in his villa where Angelotti can hide in a secret niche in the well should danger arise. A cannon shot is heard. It lets everybody know that a prisoner has escaped from the castle. Cavaradossi, determined to fight for the fugitive’s life, leads him away.

The church is filling up with people: they prepare a festive prayer service to celebrate the victory over Napoleon. In the midst of the scurry, Baron Scarpia, the Chief of Police, and his men appear. In the Attavanti Chapel, they discover a basket with food crumbs and a fan with the Marchesa’s crest, and her portrait as Mary Magdalene on the churchwall. Scarpia is certain that Cavaradossi has helped the fugitive. Tosca returns to the church disheartened: the meeting with her lover has to be postponed due to the festivities. Scarpia gallantly and masterfully fuels Tosca’s jealousy; he wants her to lead his agents to Cavaradossi and Angelotti. Tosca leaves in despair; the prayer service begins. Scarpia looks forward to a double victory: one over Cavaradossi and Angelotti, and another over Tosca with whom he has been impassioned for a long time.

Act II

Palazzo Farnese. Scarpia is waiting for Tosca. She is to come right after singing a festive cantata in honour of the victory over Napoleon in the Battle of Marengo. Spoletta appears: he was sent to follow Tosca. He informs that Tosca briefly visited Cavaradossi’s villa, where Angelotti, the criminal, has not been found, but Spoletta has arrested the artist himself.

The interrogation of Cavaradossi is futile and Scarpia commands to torture him. Tosca arrives. Cavaradossi’s moans make her reveal that Angelotti is hiding in the well in Cavaradossi’s garden. Scarpia sends Spoletta to seize Angelotti. Sciarrone announces that it was Napoleon who won at Marengo. Cavaradossi rejoices at the news.

Scarpia gives an order to execute the painter.

Tosca begs the Baron to release Cavaradossi. Enjoying her suffering, Scarpia promises to pardon the artist if Tosca becomes his mistress. Neither her fury nor her woes can soften his heart. Tosca has to comply.

Scarpia orders to fire blanks at Cavaradossi so that when the soldiers leave he and Tosca can flee together. Scarpia gives Tosca a safe-conduct pass that will help them escape from Rome without a hindrance. And yet, when Scarpia approaches Tosca to embrace her, she pierces his chest with a knife.

Act III

Castel Sant'Angelo.

Only one hour left till Cavaradossi's execution. As the artist asks his jailor to pass his farewell letter to Tosca and immerses himself in his memories, Tosca appears. She shows Cavaradossi the pass given by Scarpia and relives the murder she has committed. Cavaradossi consoles her and praises her courage.

Tosca tells him the execution will be a sham: he has to fall down as he hears the shots, and the lovers will be able to flee after the soldiers leave. Cavaradossi tries to believe the scheme and comforts his beloved, who is exhausted by all the worries of the day.

The jailor comes to fetch the artist. The guns fire, and Cavaradossi falls onto the ground. The soldiers leave. Tosca rushes to Cavaradossi but he does not respond. He is dead.

Sciarrone, Spoletta and other policemen enter. They have discovered that Scarpia was murdered. Tosca does not let them seize her: she throws herself over the edge.