Place: The garden of Don Belflor's house in Barcelona
Coraline, a former opera singer from Paris, is unhappily married to the retired bullfighter Don Belflor. She remembers how a flute-player, Tracolin, was in love with her. At this point, Tracolin himself appears in Barcelona, intent on renewing his acquaintance with Coraline. The two exchange love letters over the garden wall. Tracolin saves Don Belfor from an attack by ruffians and is invited into his house. He claims he is acting as a go-between for a dancer at the opera, Caritéa, who has fallen in love with Don Belflor. The old man is flattered but asks for further proof and Tracolin can think of no other recourse but to give him Coraline's letter. As Don Belflor is leaving for liaison with Caritéa, Coraline accuses him of adultery. In his confusion Don Belflor drops the letter on the floor. The horrified Coraline believes that she has been found out.
Coraline cannot understand why Don Belfor has not reacted angrily to the contents of the letter. Tracolin climbs over the garden wall and tells her he has been in love with her since they met at the opera. He reveals the details of her husband's adultery then leaves the garden. When Don Belflor returns, Coraline again accuses him of infidelity. He admits the truth when she mentions the name "Caritéa" and begs for her forgiveness. She accepts so long as she is allowed to keep Tracolin in the house as her lover. Don Belflor, who does not want to lose the generous dowry the marriage brought him, agrees.