Marguerite de Valois, the beautiful Queen of Navarre, who is anxious to reconcile the bitterly hostile parties of Catholics and Huguenots, persuades the Comte de Saint Bris, a prominent Catholic, to allow his daughter Valentine to marry Raoul de Nangis, a young Huguenot noble. Valentine is already betrothed to the gallant and amorous Comte de Nevers, but she pays him a nocturnal visit in his own palace, and induces him to release her from her engagement. During her interview with Nevers she is perceived by Raoul, and recognised as a lady whom he lately rescued from insult and has loved passionately ever since. In his eyes there is only one possible construction to be put upon her presence in Nevers' palace, and he hastens to dismiss her from his mind. Immediately upon his decision comes a message from the Queen bidding him hasten to her palace in Touraine upon important affairs of state. When he arrives she unfolds her plan, and he, knowing Valentine only by sight, not by name, gladly consents. When, in the presence of the assembled nobles, he recognises in his destined bride the presumed mistress of Nevers, he casts her from him, and vows to prefer death to such intolerable disgrace. The scene of the next act is in the Pre aux Clercs, in the outskirts of Paris. Valentine, who is to be married that night to Nevers, obtains leave to pass some hours in prayer in a chapel. While she is there she overhears the details of a plot devised by Saint Bris for the assassination of Raoul, in order to avenge the affront put upon himself and his daughter. Valentine contrives to warn Marcel, Raoul's old servant, of this, and he assembles his Huguenot comrades hard by, who rush in at the first clash of steel and join the combat. The fight is interrupted by the entrance of the Queen. When she finds out who are the principal combatants, she reproves them sharply and tells Raoul the real story of Valentine's visit to Nevers. The act ends with the marriage festivities, while Raoul is torn by an agony of love and remorse.