The church of Sant’ Andrea della Valle Cesare Angelotti, an escaped political prisoner and ex-consul of Rome, enters the church furtively. He lets himself into the Attavanti Chapel after finding a key that his sister has hidden for him. The artist Mario Cavaradossi enters to resume work on his portrait of Mary Magdalene, whose face is that of a blue-eyed, golden-haired woman often seen praying in the church. Although he admires the beauty of his model, he thinks only of his true love, the darkhaired, dark-eyed singer Floria Tosca. Angelotti tries to sneak away but recognizes his friend Cavaradossi who, hearing Tosca’s voice outside, gives him a basket of food and forces him back into the chapel to hide. Tosca enters, and having heard voices, is suspicious of her love and accuses her lover of entertaining a woman when he should be working. Mario assuages her fears and agrees to meet her later that night at his villa near the edge of the city. When she has gone, Cavaradossi offers his villa to Angelotti as a hideout, and the two men flee together. Baron Scarpia, the head of judicial and religious enforcement (and police) arrives with his henchmen, in search of Angelotti. They quickly discover clues that connect Cavaradossi to the woman in the painting, who is really Angelotti’s sister. Tosca leaves, focused on finding Cavaradossi who she believes is being unfaithful to her at his villa, not realizing that she has been tricked and is leading Scarpia’s agents directly to her lover.

Scarpia’s offices in the Palazzo Farnese Having followed Tosca to Cavaradossi’s villa, Baron Scarpia has the painter secretly arrested for sheltering Angelotti (still hidden within the villa). Cavarodossi is brought before Scarpia for interrogation but is led to the torture chamber when he refuses to reveal Angelotti’s whereabouts. Tosca arrives, and Scarpia questions her as Cavaradossi’s cries of agony are heard in the adjoining room. Though Cavaradossi implores her to keep silent, Tosca agrees to reveal Angelotti’s hiding place if her lover is freed. Cavaradossi, angered by Tosca’s betrayal of his friend, openly defies Scarpia, who orders his execution. As news arrives of Angelotti’s discovery and subsequent suicide, Tosca begs for her lover’s life. Scarpia names his price: her submission to his lecherous advances. Desperate, she agrees so long as Scarpia writes a letter of safe conduct for herself and Cavaradossi. Scarpia insists that there must be at least a mock execution and arranges the details with his aide that this execution will take place as they did when they “shot” Count Palmieri. Alone with Tosca, Scarpia advances amorously towards her. She stabs him with a knife she has found, takes the safe conduct pass, and rushes out to free Cavaradossi.

The Battlements of the Castel Sant’ Angelo As dawn approaches, Cavaradossi arrives at the prison of Castel Sant’ Angelo to be executed by firing squad. He sings of his love for Tosca, a love which has finally given him reason to live. Tosca appears unexpectedly with the news that his execution is to be a fake one, and that when he is “shot” he must feign death. They share a moment of joy as they look forward to their life together. The execution takes place and Cavaradossi falls to the ground. After the firing squad marches off, Tosca is horrified to discover that her lover is actually dead—she was tricked by Scarpia, and the fake firing squad death “like Count Palmieri’s” was all a ruse. Shouting is heard from inside the castle: Scarpia’s body has been discovered. Trapped, Tosca cries out, consigning both herself and Scarpia to God’s judgement, and leaps from the building to her death.