Unable to bear the yoke that an authoritarian aunt puts on her for any longer, Isabelle revolts and flees to Paris.

What can a 20-year-old orphan girl do without relationships, almost without resources, in this big city unknown to her? Isabelle studied singing. She managed to get involved in the troupe of a lyrical theatre.

Very quickly, we court her. A regular behind the scenes, the rich and cynical Henri Talaine, is trying to seduce her. He can't do it, but Isabelle is troubled...

One evening, luck came along: a singer fell ill, Isabelle replaced her as Lucie de Lammermoor. It's triumph, glory, a contract for America!

Deeply in love now, Henri suffers. "Swear to me that I will find you free in a year, when you return," he asks. Moved by her upset face, Isabelle replies: "I swear to you.

But, one year later....