Sister Angelica and two lay sisters are late for chapel. The Monitor chides them for not doing penance as Sister Angelica has done. Some of the sisters confess they still long for worldly pleasures—Sister Genovieffa for the lambs she used to tend and Sister Dolcina for sweet things to eat. Sister Angelica denies she has any such desires, but the others know she desperately longs for some word from her family. For seven years she has heard nothing from them, and the sisters speculate that she was a princess, banished to the convent for reasons they have been unable to discover. Soon alms collectors arrive, distributing the food they have gathered. One of them mentions that a magnificent coach bearing a visitor stands outside the convent gate. Angelica is startled and, with increasing anxiety, asks her to describe the coach in detail. A bell rings announcing the visitor. The Abbess enters and tells Angelica that her aunt, the Princess, has come to see her. Approaching, the Princess rejects Angelica’s gestures of affection. The Princess explains that when Angelica’s parents died, she was made guardian of both Angelica and her sister, Anna Viola, and was given control over their inheritance (“Il principe Gualtiero”). Anna Viola is to be married and the Princess demands Angelica sign her share over to her sister. Having brought disgrace on the family name, the Princess declares, Angelica is no longer entitled to any part of the inheritance. Crushed by her aunt’s cruelty, Angelica swears she has repented. She cannot, however, erase the memory of her little son, who, she learns, died two years ago. Her will now broken, Angelica sobs and signs the document. The Princess withdraws and Angelica grieves that her son died without his mother by his side (“Senza mamma”). Resolving to join her child in heaven, she drinks poison. She is then struck by the reality of what she has done and prays for salvation. A celestial choir is heard and Angelica sees a vision of the Blessed Virgin with her child.

Act I

Monica, the daughter of Madame Flora ("Baba"), and Toby, a mute boy living with them, are playing while Madame Flora is away. When she returns, she is furious that they are not ready for the seance she has planned; Monica prevents her from striking Toby. They busily prepare, and when the three guests arrive for the seance, Monica pretends to be the teenage daughter of one and the baby son of another, while Toby works the mechanical devices that control the motion of the lights and the furniture in the room. Suddenly, Madame Flora stops the seance and sends the customers away. She tells Monica she felt a spectral hand clutch her throat during the seance. She suspects Toby at first, but as Monica tries to comfort her Flora hears a voice imitating Monica's performance at the seance.

Act II

A few days later, Monica is watching Toby perform a puppet show for her; then she dances for him. Monica realizes he is trying to tell her that he loves her; pretending to be his voice, she says it for him. She runs off as Flora reenters; the medium tries cajole Toby into confessing that he was the one who touched her during the seance, or that he knows something about it. When he does not answer, she begins to whip him, but is interrupted by the doorbell. The three clients from the previous seance enter; Flora gives them their money back and tries to convince them they have been cheated, even showing them the wires and microphones, but they refuse to believe her. She throws them out, and despite Monica's protests, throws Toby out, too. Monica goes to her room, and Flora, frightened by what she has experienced, drinks herself to sleep. Toby returns; Flora awakes, and Toby hides from her; Flora, thinking he is the spirit she felt, shoots him.