A chateau near Paris, the 1920s. It is the birthday of the young, widowed Countess Madeleine. The composer Flamand and the poet Olivier are listening to the rehearsal of Flamand’s string sextet, written for the occasion, while the theater director La Roche is dozing. Flamand and Olivier realize that they are both in love with the countess. What will impress her more—Flamand’s music or Olivier’s poetry? La Roche wakes and joins the argument. Neither poetry nor music, he says, is the greatest of the arts. His own, the art of theatrical production, encompasses and overshadows them both. He believes in entertainment—splendid decor, top notes, and beautiful women, such as the famous actress Clairon, who recently had an affair with Olivier. La Roche is to direct the poet’s new play, with Clairon and the countess’s brother, a talented amateur actor, in the leading roles. As the three men leave to prepare for the rehearsal, the count and countess enter, teasing each other about their artistic opinions.
La Roche and his protégés return and Clairon arrives for the rehearsal. She and the count read a scene from Olivier’s play that ends with the count reciting a passionate sonnet. La Roche leads them both off to rehearsal, leaving Flamand and Olivier alone with the countess. Olivier declares that the sonnet was written for her and recites it again, which inspires Flamand to rush off to set it to music. Olivier seizes the opportunity to declare his love to the countess, who still hesitates between poetry and music. Flamand triumphantly returns to sing the sonnet he has just composed. The countess reflects on the synthesis of words and music, while Olivier, though moved, feels that his work has been ruined. The two men argue about the true authorship of the sonnet, and the countess decides the issue: it is now hers.
When La Roche takes Olivier away to rehearsal, Flamand in turn declares his love to the countess. He asks her to decide: music or poetry, him or Olivier? She promises that he shall have the answer the next morning at eleven o’clock. Flamand leaves in great excitement.
The rehearsal over, the participants return. Flamand and Olivier resume their argument of words versus music and the others join in. The count ridicules opera in general. La Roche introduces a pair of Italian singers who perform a duet. Then he announces his plans for an epic, mythological spectacle, to be given for the count’s birthday. When the others make fun of his grandiose ideas, La Roche eloquently attacks them, expressing his theatrical creed: instead of the feeble attempts of modern writers, he wants drama to show human beings in all their complexity, as creatures of flesh and blood. He challenges Flamand and Olivier to create new works that will speak for their time. His listeners are moved and a new plan emerges: Flamand and Olivier are to write an opera together. Possible subjects are discussed, until the count suggests that the events of this very day should be the subject, with the people present as its characters—it is the opera we have been watching. The ending is yet to be decided by the countess.
The company breaks up and the guests leave for Paris, accompanied by the count. Servants enter to tidy up the room, commenting on the events of the afternoon from their point of view—isn’t everybody just playing theater? Monsieur Taupe, the prompter, who had fallen asleep during the rehearsal, unexpectedly appears. He explains to the major-domo that, in fact, it is he who is the most important person in the theater because without him the show couldn’t go on. The major-domo, after listening patiently, arranges for his transport home.
It is evening. The countess enters and learns from the major-domo that Olivier will call the next morning at eleven to hear from her the ending of the opera. She tells herself that since the reading of the sonnet, the composer and the poet seem inseparable—now they even expect to meet her the following morning at the same time. She begins singing the sonnet to herself, trying to make up her mind: which of the two men does she love? Looking at herself in the mirror, she realizes she can’t make a choice. When the major-domo announces that dinner is served, she smiles at her reflection and slowly walks out of the room.