Paris, 1930s  

The wealthy Rambaldo and his mistress, Magda, are hosting a cocktail party. Prunier, a poet and also the boyfriend of Magda’s maid Lisette, declares that true love is back in fashion. He sings a ballad about a girl who turns down a king for real love, and Magda makes up a second verse about how the girl falls in love with a poor student. She then reminisces about her first experiences of love as a young girl at Bullier’s, a famous Latin Quarter dance hall. Prunier reads Magda’s palm and predicts that she will go south in pursuit of romance and happiness, just like ‘la rondine’, the swallow.  

Rambaldo introduces a visitor, Ruggero, who is new to Paris and wants to know where to spend the evening. They recommend Bullier’s, and Ruggero leaves to go there. After the rest of the guests have left, Prunier returns in secret to escort Lisette to Bullier’s. Magda decides to stay at home, then changes her mind. She disguises herself and leaves for Bullier’s too, risking it all…  

Bullier’s, Paris 

The nightclub is packed. Ruggero is sitting alone. Magda enters and joins Ruggero, who doesn’t recognise her in the disguise. She introduces herself as ‘Pauletta’. When she teases him about his probable love affairs, he replies that should he ever love a woman, it would be forever. While they talk and dance, they realise that they have fallen in love with each other.    

Prunier and Lisette arrive. Lisette is astonished by the sight of Magda, but Prunier, understanding the situation, convinces her that it is someone else with a chance resemblance. Suddenly Rambaldo appears, and Prunier asks Lisette to keep Ruggero out of sight. Rambaldo demands an explanation from Magda for her behaviour. She replies that she has found true love and is going to leave him. Rambaldo expresses hope that she will not regret it. Ruggero returns and Magda leaves with him to start a new life… 

The French Riviera  

Magda and Ruggero have been living in a villa on the Riviera, but their money is running out. Ruggero says that he has written to his mother for help, and for permission for them to marry. He imagines what their idyllic family life would look like, but Magda is uncomfortable that Ruggero does not know about her past as a courtesan.  

He leaves, and Prunier and Lisette arrive, arguing. He had tried to make her a singer, but it had been a disaster. Magda tells Lisette she would be happy to take her back as a maid. Prunier delivers a message from Rambaldo: he is willing to welcome her back as his mistress. Ruggero returns with a letter from his mother, who is delighted that her son has found a good and virtuous bride. Unable to keep her secret any longer, Magda confesses that she can never be his wife because of who she really is – her reputation would ruin his future. She packs a suitcase and, like the swallow, she flies away…