Boston and its vicinity at the end of 17th century. Riccardo the governor of Boston, is in love with Amelia, wife of his friend and secretary Renato. The fortune teller Ulrica foresees Riccardo's death at the hand of a friend; this proves to be Renato, who mistakenly believes his wife has been unfaithful to him, and so joins in a plot to murder Riccardo at a masked ball. As he is dying, Riccardo declares that Amelia is innocent, and forgives his enemies.