ACT I: The Church of Sant'Andrea della Valle in Rome, 1800. Noon.
Angelotti, a political prisoner, has escaped from Castel Sant'Angelo and takes cover in the church where his sister, the Marchesa d'Attavanti, has left him the key to the family chapel. He is discovered by the painter Mario Cavaradossi, a liberal sympathizer, who is painting an altarpiece. His portrait of Mary Magdalen is inspired by the Marchesa, whom he has observed in prayer. When the singer Floria Tosca, Cavaradossi's lover, arrives, she recognizes the blue-eyed Magdalena as none other than the Marchesa herself. Tosca jealously insists that the figure be made to look more like her dark-eyed self, and leaves the church. Soon after, a cannon shot from the prison announces Angelotti's escape and Cavaradossi hurries him away to hide in his country villa.
The Sacristan tells the choir of the reported defeat of Napoleon at Marengo, to be celebrated with a High Mass. Their jubilation is interrupted by Scarpia, the feared Chief of Police, who arrives with his men to search for Angelotti. Scarpia finds a fan with the Attavanti crest, part of a disguise left for Angelotti, as Tosca returns to tell Mario that she will sing for the Queen that night at the Palazzo Farnese. Scarpia uses her jealousy to sow seeds of doubt about her lover and the Marchesa; as Iago used a handkerchief to manipulate Othello, he will trap Tosca with the Marchesa's fan.
ACT II: Scarpia's apartments at the Farnese Palace. That evening.
Scarpia desires Tosca, and hopes to use the arrest of her lover to force her to his will. As he dines in his room, he hears Tosca's voice rising from the celebrations below. Spoletta arrives from Cavaradossi's villa, having failed to find the escaped Angelotti. He has, however, arrested Cavaradossi and brings him before Scarpia.
Tosca, having been to the villa as well, knows that Scarpia was lying about Mario's infidelity. She also knows the hiding place of Angelotti, which she reveals when Mario screams under torture. Scarpia proposes a bargain to Tosca: If she will yield to him, he will spare Cavaradossi, and give them both safe conduct out of Rome. But, for political reasons, he first must hold a mock execution. Tosca agrees, and as Scarpia prepares to collect his reward, she offers him a deadly surprise.
ACT III: The battlements of Castel Sant'Angelo, high above the Tiber. Near dawn.
Cavaradossi, awaiting execution, recalls his first night with Tosca — when the stars shone just as they do now. Tosca arrives with the safe-conduct, and describes how she obtained it. A carriage is waiting, and she has brought money and her jewels. She explains that Mario will have to feign death at the hands of a mock firing-squad, and coaches his acting.
The firing-squad, however, is real; Scarpia has worked his evil from beyond the grave. Pursued by Scarpia's minions, who have discovered her deed, Tosca calls on her tormentor to meet her before the Throne of God, and leaps to her death.
Courtesy of Opera Theatre of Saint Louis