On 30 May 1770, Paris finished celebrating the wedding of the dauphin of France (the later Louis XVI) and Marie-Antoinette with a grand display of fireworks. The festivities, however, suddenly turned tragic: a few cases of rockets were ignited and a fire broke out. The crowd was overcome by panic, and the people trampled each other as they attempted to flee, leaving many dead behind.
Scene 1 – The library of the castle of the Marquis de la Force at the end of April 1789, a few months after the outbreak of the French revolution
The Marquis de la Force is awakened from his afternoon nap by his son, the chevalier, who has just received word that the carriage carrying his younger sister, Blanche, was stopped by a crowd of malcontents on the way home. The chevalier's concern is not groundless: the embittered French people have been revolting against the aristocracy more and more vehemently. In addition, Blanche was born with an extremely fearful nature, and any tiny thing or idea can fill her with dread. The Marquis de la Force recalls the tragic circumstances of Blanche's birth: the carriage bearing the pregnant Marquise de la Force had got stuck in the crowd in the panic that broke out at the fireworks organised around the dauphin's wedding; after returning home, the upset woman brought her daughter into the world prematurely and died in childbirth herself.
Blanche returns home safe and sound. She attempts to project a face of calm for her father and worried brother, and then retreats to her room to rest. Presently, she is heard screaming: the footman's shadow has startled her. Distraught, she goes back to ask her father to allow her to flee this terrifying world by joining the Carmelite Order.
Scene 2 – The parlour of the Carmelite Convent at Compiègne
Blanche is admitted into the convent by the now-elderly and ailing prioress, Madame de Croissy, who questions the girl to find out why she wants to become a nun. She warns Blanche that the order is not a refuge, nor is it an organisation for the mortification of the self, but rather a house of prayer. It is not Blanche's strength that God will put to the test, but her weakness. The girl stands by her desire to enter the order.
Scene 3 – In the convent
The ever cheerful Sister Constance is chattering animatedly to the new novice Blanche, who nevertheless feels that these high spirits are not proper when the prioress is dying. Constance, however, is not afraid of death, believing that it will be just as amusing as life is; anyway, she has always wanted to die young. Blanche is astonished by Constance's fearless serenity, and envies her. Constance confesses to Blanche that when she first saw her, she felt that they would both die young, and together. Blanche is frightened and angered by the thought.
Scene 4 – The convent's infirmary
The prioress is dying. She confides to her sub-prioress, Mother Marie of the Incarnation, that of all her girls, it is Blanche that she worries about most, and she makes the sub-prioress swear that she will always look out for the girl. Blanche comes before the prioress to receive advice and a blessing from the head of the order. Nothing can ease the awful pain the prioress is suffering: neither God nor the doctor. She is left along with her fear of death. In her terrible agonies, she sees a vision of the convent's chapel in ruins, as if God himself has abandoned them. Finally, she whispers something else to Blanche, and then, at the end of her horrible torments, falls dead.
Scene 1 – The convent's chapel. Night-time
Constance and Blanche have finished their shift sitting vigil beside the dead body of the prioress; Constance leaves her companion to summon their replacements. Blanche is overcome by fear and is about to flee from the chapel when Mother Marie enters: originally planning to rebuke the terrified girl, her heart softens and she absolves her of all other duties for the day.
Interlude – The garden of the convent
Blanche and Constance discuss the death of the prioress. As Constance sees it, the Good Lord has given the prioress a particularly difficult death – perhaps somebody else's death. “Nobody dies for themselves, but rather for others, or instead of somebody else,” she says.
Scene 2 – The convent's chapter house
Madame Lidoine, the new prioress is holding forth to the nuns: she reminds them that – even in these difficult times – the chief duty of servants of God is prayer: they must beware of anything that distracts them from this, including the grace of martyrdom.
Interlude – In the convent
A clamour fills the nunnery: the Chevalier de la Force has arrived to visit his sister before journeying abroad to flee the revolution. The prioress permits the visit, but instructs Mother Marie to be present during the conversation between Blanche and the chevalier.
Scene 3 – The parlour of the convent
The chevalier has come to relay their father's message to his sister: because of the anti-clerical decrees dictated by the revolution, he is afraid that Blanche is no longer safe in the convent. The girl, however, is not willing to leave the order: she is now a daughter of Carmel, who must fight in her own way during these difficult times. The chevalier hardly recognises his fearful younger sister in the determined woman he sees before him. After the man departs, the upset Blanche is comforted by Mother Marie.
Scene 4 – The convent's sacristry
Pursuant to one of the revolutionary decrees, all Catholic priests must leave their offices and their quarters. This includes the Carmelite chaplain, who gives a farewell blessing to the nuns. The worried Blanche asks the priest what he is going to do. The chaplain reassures her that he is going to continue his ministry in secret and will stay close to the Carmelites. After the priest departs, the distraught nuns debate the increasingly menacing revolutionary situation. Mother Marie believes the daughters of Carmel have only their lives to give for their church. The prioress, however, corrects her: in her opinion, it is not her place to decide if they will be worthy of the grace of martyrdom, but God's alone. Soon the priest returns: the angry crowd is heading for the convent. He has to flee in a different direction. The nuns open the gate for the crowd. Two commissioners enter the nunnery to announce that, pursuant to the Legislative Assembly's decision of 18 August 1792, all religious quarters in the country are to be vacated. After the commissioners depart, Mother Jeanne attempts to comfort the terrified Blanche with a statuette of the Christ Child, but the howling of the crowd alarms the girl, and the statuette drops from her hand and shatters on the ground.
Scene 1 – The chapel of the convent
The prioress has been required to travel to Paris. In her absence, the chaplain and the nuns gather in the destroyed chapel. At Mother Marie's behest, they conduct a secret vote to decide if they should take a vow of martyrdom. One dissenting vote is cast – and this is sufficient to defeat the plan to take the vow. Everybody believes that Blanche was the dissenter, but Constance states that she was the one who voted “no”. However, she has since changed her mind and now accepts the vow. The sisters go before the chaplain to take the vow. Blanche is overcome by fear and flees.
A commissioner informs the Carmelites that they may no longer maintain any relationship with “enemies of the Republic” and that it is forbidden for them to practice their religion; in exchange, they may live “free” lives outside the convent. The prioress rebukes Mother Marie for taking a vow of martyrdom with the nuns in her absence.
Scene 2 – In the library of the Marquis de la Force
In her father's ruined castle, now occupied by the people, Blanche hides disguised as a maidservant. Then Mother Marie enters the room wearing ordinary clothing; she has come to take the girl to a safe place, but Blanche does not dare to go with her. The marquis was guillotined a few days earlier, and she herself is now living in terror and despises herself for it. Mother Marie gives the girl an address and encourages her to go find it.
Interlude – One of the streets in the quartier Bastille
Blanche learns from an old lady that the Carmelites have been arrested in Compiègne.
Scene 3 – One of the prison cells in the Conciergerie in Paris
With the exception of Mother Marie and Blanche, the Carmelites are awaiting their sentence in Paris. The prioress takes responsibility for deciding on the fulfilment of the vow of martyrdom. Constance has dreamed that Blanche will return to them. A prison guard enters and announces the resolution of the Revolutionary Tribunal: the nuns have been condemned to death. The prioress gives her girls permission to fulfil their vows of martyrdom.
The chaplain informs Mother Marie that the sisters have been condemned to death and will soon be executed. The despairing Mother Marie starts off to join her companions, but the chaplain holds her back: in his view, it is God's will for Mother Marie to remain alive.
Scene 4 – At the Place de la Révolution in Paris
The crowd watches reverently as the nuns from Compiègne arrive for the execution. Singing the Salve Regina, the sisters go to the guillotine one by one. Constance is the last one to go to the scaffold, but before the blade comes down on her, she notices Blanche out in the crowd. She meets death with a contented smile on her face. With complete calm, Blanche walks over to the guillotine and dies a martyr's death herself.