ACT I
Scene i
The governor’s mansion
Riccardo, the governor of Boston, is giving an audience. Oscar, his page, brings him the list of guests invited to a masked ball. Riccardo is overjoyed to see included the name of Amelia, the wife of his secretary Renato, with whom - despite his conscience¬ - he is in love. The faithful Renato tells him of a plot against his life but Riccardo brushes the warning aside. A judge arrives with papers to sign, banishing a fortune-teller named Ulrica for her evil influence. Oscar intercedes for her. Riccardo, for a lark, suggests that they all go in disguise to see the sorceress and test her powers. The conspirators, Samuel and Tom, fall in with the scheme, seeing in it an opportunity to carry out their plot against Riccardo.
Scene ii
Ulrica's place
Silvano, a sailor arrives, asking Ulrica if the many years he serves the governor will be rewarded and the fortune teller promises him wealth and promotion. Riccardo, disguised as a fisherman, hears the prophecy and puts money and a promotion letter in Silvano’s coat. Everybody rejoices once the prophecy becomes true aside of Ulrica who senses that her work was interrupted by someone else. Amelia comes to consult the fortune-teller. Concealed, Riccardo hears Amelia ask for a magic potion, which will uproot the love from her heart. Ulrica tells her of such a herb which can only be gathered at midnight in the place where the gallows stands. When Amelia leaves, Riccardo asks to have his fortune told. Ulrica tells him he will die by the hand of the friend who will next shake his hand. Renato enters. Riccardo goes forward and grasps his hand. He tells the fortune teller that this is the hand of his most trusted friend.
ACT II
Midnight, in a deserted field, beside the gallows
Amelia, veiled, comes to pluck the magic herb, when Riccardo arrives. They proclaim their love to each other but Amelia begs Riccardo to leave her. At that point Renato comes into view. Amelia, seeing her husband, lowers her veil in fright. Renato has come to warn his master that conspirators are lying in wait for him. Riccardo consents to escape through a side path but asks Renato to promise that he will escort the veiled Amelia back to the city without attempting to find out who she is. As they leave Renato and Amelia fall into the hands of the conspirators who, enraged at the loss of the governor, insist at least on knowing his sweetheart. They try to pull off Amelia's veil. Renato draws his gun. To stop bloodshed Amelia reveals herself. The stunned Renato sees his own wife.
ACT III
Scene i
Renato's house
Renato prepares to kill his wife. Amelia begs to embrace their son before she dies. When she goes out Renato gazes at the portrait of Ricardo which hangs on the wall and decides it is he on whom he must vent his wrath. He joins Samuel and Tom in their plot to murder the Governor. They draw lots; Amelia is commanded to pick the paper from an urn. It bears the name of Renato. The page Oscar arrives with the invitation to the masked ball.
Scene ii
A ballroom in Riccardo's mansion
Riccardo decides to give up Amelia and send her and Renato abroad. Doors open. Renato learns from Oscar what disguise Riccardo is wearing. Amelia also recognizes Riccardo, begs him to flee his impending death, but he refuses. As they bid each other farewell, Renato, unobserved, comes between them and shoots Riccardo. Too late, Renato hears from the dying ruler of Amelia’s innocence. With his last words Riccardo pardons Renato and all the other conspirators.