The opera opens on the Church of Sant’Andrea Della Valle where Cesare Angelotti, the former Consul of the Roman Republic, has escaped from prison. Angelotti hides in the private chapel of the church because his sister, Marchesa Attavanti, left a key for him at the feel of the Madonna statue. After Angelotti has hidden, the Sacristan begins cleaning the church. Mario Cavaradossi, a painter, arrives to continue his work on a painting of Mary Magdalene. The Sacristan comments that the painting could be a representation of a woman who has recently come to the church to pray every day (Angelotti’s sister). Cavaradossi sings of the contrast of this blonde Mary and his dark-haired love, Floria Tosca, the singer (Recondita armonia).
After the Sacristan has left, Angelotti comes out and greets his friend, Cavaradossi, and informs him that the Chief of Police, Scarpia, is searching for him after his escape from prison. Cavaradossi assures him that he will lend his help, when Tosca is heard screaming his name outside. Angelotti hurries to hide, taking a basket of food that Cavaradossi gave him. Tosca comes in quickly to ask what Cavaradossi has been up to, suspicious that he has been with another woman. Cavaradossi attempts to convince her that he is faithful, and Tosca asks him to take her to his villa that evening (Non la sospiri, la nostra casetta). Seeing the painting, Tosca becomes jealous again, recognizing the woman as the Marchesa Attavanti. Cavaradossi explains that she has been praying quite often in the church, and he simply must have subconsciously painted her. Distracting her, Cavaradossi then tells her that she has the most beautiful eyes in the world (Qual’occhio al mondo). Tosca leaves, and Angelotti comes out of his hiding place and tells Cavaradossi that he plans to escape dressed as a woman, using clothes that his sister left him. Cavaradossi gives Angelotti the keys to his villa, and tells him to hide in the garden well. A canon sounds that