Back story
Magda, an orphan, grew up with an old aunt in Paris. When she was seventeen, the shy girl ran away for an evening and found her way to the Café Bullier, a dance hall where young students as well as rich bankers and pleasure-seeking widows meet. That evening Magda met a young student and they both fell in love. But Magda suddenly became afraid of her own courage, head over heels, left the student in the café and ran back to her aunt.

Many years have passed since then and she has never been able to get the student out of her mind. Her life was not as romantic as she had hoped. She was denied a profession of her own, and finally she had to capitalise on her beauty. The rich gentlemen of Parisian society now adorned themselves with her like a trophy, and so she passed from hand to hand. Now she has been the courtesan of the banker Rambaldo for some time, who offers her a life of luxury. She gives him her body in return, but not her feelings.

Act One
In the flat that Rambaldo puts at her disposal, Magda de Civry, as she is known in Parisian society, gives an afternoon reception. The guests are Rambaldo, his business associates and their female companions, young women whose lives have been no different from Magda's. Also invited that afternoon is the poet Prunier, an acquaintance from the days when she still moved in artistic circles and money played no role in her life. Prunier improvises a romance in front of the guests about the steadfast Doretta, who does not allow herself to be seduced by the king and his wealth. When he breaks off in the middle of his recital, Magda spontaneously invents the ending of the song. Doretta would one day find happiness in the arms and kiss of a young student. Everyone is impressed and almost a little affected by the passionate and unexpected devotion that the otherwise reserved Magda suddenly displays.

She reveals the secret behind this outburst to her friends and tells them the story of her youth, when for a few hours she discovered the happiness of love with the young student in the Café Bullier. While the women retire to an adjoining room where the poet Prunier is busy predicting their future, Rambaldo receives a young man, the son of a business friend from the province of southern France. While Magda is still following Prunier's prophecy that her life will be like that of a swallow, a «rondine», namely like a journey towards the light and happiness with a return to an uncertain future, her friends take care of the young provincial Ruggero. They give him advice on where best to spend the first evening in the cosmopolitan city of Paris. Finally, the maid Lisette speaks up: the best place to have a good time is the legendary Café Bullier. Suddenly all the guests set off to plunge into Paris at night.

Almost without noticing it herself, Magda had been watching young Ruggero, and memories of the experience with the young student she had met at the Café Bullier rise up in her again. She wants to return to the past, relive the moment of that time and transform herself into the girl from back then. She sets off for the Café Bullier. The maid Lisette also has an evening out. She has arranged to meet the poet Prunier. She is, even if he is embarrassed for her, his muse, whom he loves. The two of them also set off to go out in Paris, Lisette having secretly helped herself to her mistress Magda's wardrobe for the evening out.

Act Two
At the Café Bullier, Magda meets the young man she had only seen from a distance a few hours earlier in her salon. He, Ruggero, had hardly noticed her and does not recognize her.  Both are fascinated by each other and the magic of Café Bullier begins to work. They find each other in the dance and can't let go of each other. He asks her her name, she not only conceals her real name, but also gives him nothing more about herself, while he happily tells her about life in his home town of Montauban. Both also meet Prunier and Lisette in the café. Lisette thinks she recognises her mistress Magda, but is completely taken aback when Ruggero introduces her as his girlfriend Paulette. All four give in to their illusions, dreams, and toast to love, or rather to life, which in turn gives them love.

But Magda has an awakening when she realises that she is being secretly watched by Rambaldo. As Prunier manages to distract Ruggero, Magda and her financier Rambaldo come to a confrontation. In an act of superhuman effort, she renounces Rambaldo and her previous life. She wants to realise her lifelong dream and experience the happiness of love with Ruggero, to make up for what she missed years ago. Rambaldo withdraws. Magda trembles with happiness in Ruggero's arms and can hardly believe the decision she has just made.

Act Three
Magda and Ruggero have now been spending several weeks in a hotel near Nice. Magda is still trying to maintain the illusion of happiness, but Ruggero is more realistic and has secretly contacted his parents to help him and his new girlfriend out financially. One late summer morning he finally informs Magda of this - and says even more, namely that he has asked his parents to agree to marry her. Magda, who still keeps quiet about the life she has led, suspects that her dream of great happiness will soon end. While he describes his dream to her, life in a small town with a house, a garden and a child, she realises that she must end this relationship. But she is not yet ready to do so. Prunier has found out where Magda is and wants to help her get back to her former life. He comes with news from Rambaldo that he would forgive her and is ready to «support» her again. Prunier wants to convince Magda that it is the right thing for her to return to Rambaldo. He and Lisette had also come to an arrangement, and he had to realise that he could never make an avant-garde artist out of a woman who felt born to be a maid. Magda asks Prunier to spare her this advice. An intimate friendship comes to an end.

When Ruggero finally arrives overjoyed with a letter from his mother welcoming her son's wish, who has surely found an honourable and virtuous girl, Magda finally breaks her silence and makes it clear to Ruggero that they must separate. She has lied to him and can never be the wife he imagines. Although they love each other, Magda breaks away from Ruggero, who hardly understands what is going on. Magda goes back to her former life, back to her luxurious existence, to her pain and her dreams... and already it seems that her love with Ruggero was only a dream, too.

Written by Christof Loy