A room in the governor’s house
In the morning numerous petitioners wait for the governor, count Riccardo, to arrive into his office. Riccardo starts reading all the documents, but his attention is quickly distracted by the guest list of his upcoming ball, where he notices Amelia’s name. The mere thought of seeing her again makes him dream. So when his friend and most trusted advisor Renato, who is also Amelia’s husband, enters the room, Riccardo worries he might suspect his feelings. But Renato came to warn Riccardo of a threatening conspiracy against him. Riccardo ignores the threat, he doesn’t even want to know his enemies’ names, as he relies on the love and protection of his people.
The highest judge handles the governor some papers to sign, among which an order to condemn the fortune-teller Ulrica. But Oscar, Riccardo’s page, defends Ulrica and highlights that all her prophecies have turned out to be true. Deciding to see for himself, Riccardo invites everyone to visit Ulrica’s cave in disguise at exactly three o’clock.
At the fortune-teller’s cave
Surrounded by women from the thereabouts, Ulrica invokes the dark spirits. Riccardo, disguised as a fisherman, enters loudly in the cave, but the women push him at side. Ulrica foresees to a sailor named Silvano that he will soon earn receive money and a promotion. For his own amusement, Riccardo immediately slips into Silvano’s haversack the money and a promotion note. As Ulrica sends everybody away to welcome Amelia, Riccardo secretly stays to eavesdrop on their conversation. Amelia begs for help to cure her adulterous feelings for another man. Ulrica sends her to pick some miraculous herb by the gallows at midnight. Amelia is frightened, but determined to protect her faithfulness. Riccardo decides to follow Amelia to keep her safe.
Riccardo’s court men in disguise arrive at Ulrica’s cave. The count asks Ulrica to have his fortune told, but, when Ulrica reads his palm, she sees he’s a noble man and a great warrior. She predicts a soon-to-be death, not in the battlefield, as he would assume, but by the hand of a friend. It will be the next person who shakes his hand. Riccardo makes fun of Ulrica’s prediction and he offers his hand to all those present, but nobody dares to take it. At this moment Renato arrives, unaware of the prophecy, and clasps Riccardo’s hand in greeting, thereby revealing the governor’s identity. Riccardo is now convinced of the fortune-teller’s fraud, because Renato is his closest friend whom would never hurt him.
A lonesome field next to the gallows
Amelia arrives at midnight at the gallows. Although she is daunted by the scary landscape, she is determined to find the herb that Ulrica had told her about. Riccardo, who had followed her, makes her confess her love to him. Jubilating, Riccardo is ready to sacrifice even his friendship to Renato, but Amelia is torn between duty and desire. Unexpectedly Renato shows up to warn the governor of the approaching conspirators, ready to end his life. Amelia covers herself with a veil before her husband can catch sight of her. Renato and Riccardo exchange their coats so the governor is able to remain unrecognized. Riccardo fleas, but not before making Renato promise to take the veiled woman safely back to town, not talking to her and not asking her identity.
Renato and Amelia fall into the hands of the conspirators, who are surprised to see Renato instead of Riccardo. They want to know who the mysterious woman is. Renato takes up arms in order to protect her, but Amelia interferes by dropping her veil. Renato has to face the fact that his friend’s secret lover is nobody else than his own wife, Amelia. He is exposed to ridicule. He asks Samuel and Tom to meet him the very next day.
Renato’s study room
After trying in vain to explain her innocence to her husband, Amelia gives up on hope and waits for her death. She asks to see their son before she dies and Renato grants her wish. Now alone, he comes to the conclusion that it is Riccardo whom should be punished with death and not his wife. He informs Samuel and Tom that he will join the conspiracy. They decide to draw lots to determine who will kill Riccardo, and Renato forces Amelia to choose from the slips of paper. His own name comes up.
Oscar brings the invitation to the masked ball. Renato deems this celebration to be suitable for the attack. Amelia suspects what the three men are plotting and intends to warn Riccardo.
Riccardo’s study room
Riccardo decides to keep his promise and to renounce his love to Amelia. Agonizing, he signs the decree to send Renato and his family in England. Oscar hands him over an anonymous letter in which the count is warned about an attack on the very same evening. Riccardo plans to attend the ball anyway. He can only think about saying goodbye to Amelia forever.
The ballroom at the palace
At the ball Renato learns from Oscar what costume Riccardo is wearing. Amelia already recognized him in disguise and tries to convince him to getaway as soon as possible. Riccardo still ignores the warning – he explains his decision and bids her a last farewell. At the very same moment Renato stabs Riccardo with a dagger.
The count orders for his assassin to be released. Riccardo assures his friend, Renato, that Amelia is innocent, that she never broke her marriages vows. Renato realizes his absurd jealousy, but his remorse is now in vain.