In May, 1770, the people of Paris were celebrating the wedding of the Dauphin of France to Marie Antoinette. The Marquis de Ia Force and his wife were on the way home in their carriage when some of this throng panicked and, surrounding the coach, broke one of its windows. The pregnant Marquise became terrified and, a few hours after being rescued from the mob by soldiers, died following the birth of a daughter Blanche.

The Marquis is taking a nap in his library when his son arrives with news that the people are rioting in the streets and that Blanche is somewhere among them. The Marquis remembers what happened to her mother and is worried. The Chevalier is more worried about what the excitement will do to her nerves, for she has always been prey to fear (he calls her “little rabbit”), but the Marquis believes that a good marriage will cure her. Blanche enters, exhausted by her experience with the crowds, and asks to go to her room. Brother and sister exit, but Blanche returns, in terror, having seen a strange shadow. She tells her father that she wants to join the Carmelite order because she can no longer live in the world.

The Prioress of the Convent tries to determine whether Blanche is genuinely interested in becoming a nun and, so, speaks strongly to her. She is satisfied by Blanche’s determination and is greatly moved when Blanche unconsciously chooses the name she herself had considered using, “Sister Blanche of the Agony of Christ.”

Blanche and Sister Constance are talking together: Blanche cannot understand why her friend is so gay when the Prioress is so ill. Sister Constance says she would gladly give up her life for the Prioress. Blanche, with her fear of death, cannot accept this thought and, when Sister Constance further says that she believes they will both die the same day while still young, Blanche becomes angry.

The dying Prioress has come to fear the approach of death. Feeling a strange kinship to Blanche, she blesses the girl. Then begins her death agony, and in her delirium she sees the desecration of the convent.

When Blanche is left alone to pray over the body of the Prioress, she is overcome by her fears and tries to run away. Mother Marie stops her and comforts her.

Constance expresses to Blanche her belief that the Prioress’ suffering at death was the more acute because she was dying for someone else, someone who would find it easy to die when his turn came.

The new Prioress arrives and delivers her first talk to the sisters.

The Chevalier comes to see his sister, and the new Prioress asks Mother Marie to be present during the conversation. The Chevalier asks Blanche to come away with him, as the revolution is spreading. Blanche refuses, and her brother accuses her of being afraid to leave the convent. She says she is no longer free to choose. But after he leaves, she gives way to fear, and Mother Marie comforts her.

The Chaplain is no longer allowed to say Mass and takes leave of the sisters. A mob outside, however, blocks his escape, and he is forced back. Soldiers enter, and a commissioner reads an order expelling the Carmelites. After the soldiers leave, Mother Jeanne gives Blanche the figure of the Christ child for courage, but, on hearing the mob outside, Blanche drops it, and it shatters.

In the devastated chapel, Mother Marie, who is in charge because the Prioress is in Paris, asks the sisters to take a vow of martyrdom. The vote must be unanimous, but there is one vote against it. Everyone is convinced it is Blanche’s, bur Sister Constance confesses co it and then retracts it. As the sisters kneel co take the oath, Blanche, overcome with terror, flees the chapel. The nuns must leave the chapel divested of their religious garb and are led away by Mother Marie.

Blanche is now a servant in her old house, taken over by others after the execution of her father. Mother Marie comes to ask Blanche to return to the Order, but Blanche is too afraid to agree. Later Blanche hears news of the sisters’ arrest.

In prison, the Prioress comforts the nuns and joins them in their vow of martyrdom. Sister Constance is certain that Blanche will return. The Revolutionary Tribunal condemns the nuns to death.

On encountering the Chaplain, Mother Marie learns of the order for the nuns’ execution and wishes to join her sisters, but the Chaplain argues against it: her suffering will be not to die.

At the guillotine the nuns ascend the scaffold singing the Salve Regina. Their chant is weakened as one voice after another is silenced. When only one voice remains, that of Sister Constance, Blanche emerges from the crowd and takes up the hymn. Fearlessly, she mounts the scaffold.