The story is set in a convent; this is where Sister Angelica took her vows seven years earlier in order to escape from the world, after having given birth to an illegitimate son. Some sisters are hurrying to church for evening prayers; two lay sisters are late, and also Sister Angelica, who makes an act of penance before entering church. After prayer and before recreation, Sister Zelatrice hands out punishments: to the two lay sisters who didn't make the act of penance as they were late, to Sister Lucilla who laughed in church and to Sister Osmina who had two roses hidden in her sleeves. Now the sisters approach the fountain and observe with joy, almost as though it were a miracle, the beam of sunlight that lights up the water, an event that happens only three times a year. They decide to take a bucket of the golden water to the tomb of Sister Bianca Rosa, who certainly desires it; they, on the other hand, aren't allowed to have desires. But Sister Genovieffa confesses quite candidly that she'd still love to hold a small lamb in her arms, while Sister Dolcina can't resist culinary delights. And Sister Angelica? She denies that she has any desires, but the other sisters aren't convinced and mutter that their companion has a great desire to see her noble relatives again, whom she hasn't seen of heard of for seven long years. Their chatting is suddenly interrupted by the arrival of Sister Nurse, who asks Sister Angelica to get a remedy for Sister Chiara, who's been stung by a wasp. Sister Angelica finds the remedy from among the plants she tens and gives it to the nurse, while the two mendicant sisters arrive with a mule. They are immediately surrounded and hand around what they've collected through begging; one of them asks if there's someone in the parlour as they noticed a rich carriage outside the convent door as they arrived. Sister Angelica becomes tense: she passionately wishes that the visit is for her. In fact, the Mother Superior appears at this point and calls her to the parlour: her aunt, the Princess, wishes to speak with her.
Trembling with emotion, Sister Angelica goes up to her aunt, who, with an air of icy indifference, informs her that Angelica's younger sister is soon to marry and so she has come to get her to sign a document concerning the partition of the family fortune. Who is her sister going to marry?, asks Sister Angelica. She will marry a person who, through love for her sister, - replies her aunt - has forgiven the great fault with which Angelica has stained the family honour. Sister Angelica momentarily rebels against the unbending severity of her aunt, then reaffirms her will to expiate her sins, but expresses one desire: she wants to hear about her son, whom she only saw at the moment of his birth and since then she hasn't heard anything about him, for seven long years. After a few moments of silence, her aunt the Princess tells her that her child died two years earlier. Sister Angelica sign the document and, immobilised by grief, remains along, crying out for her son whom she'll never hold in her arms again. The other sisters return and they all head off for their cells for the night. After a little while, however, Sister Angelica leaves her cell and starts collecting flowers. She uses these to prepare a poisonous potion; then she embraces the cross, gets ready to die and invokes the Virgin Mary for pardon. Suddenly she hears the voices of angels and the church lights up; the door opens and she sees the Queen of Comfort who pushes towards her a belong little boy, dressed in white: it's her son and Sister Angelica dies embracing him.