As the discomfited Don Juan turned angrily aside, he encountered a lady in deep mourning and a cavalier, who had just entered the grounds; and as he greeted them, he saw, to his dismay, that they were Donna Anna and her betrothed, Don Octavio. However, Anna did not at first recognise in him her father's midnight slayer; and having come with her lover to ask Don Juan's help in finding the villain who had brought such misery upon her, the pair quickly made known their quest, and the double-dealing cavalier promised to give them his aid.
But whilst they were thus talking together, Donna Elvira returned, and declaring earnestly to the two strangers that Don Juan was a false villain, implored them not to place any faith in his promises. Don Juan, coolly announcing that Elvira was a mad-woman, pretended to try and soothe her frenzy; but the poor lady, stung by this fresh outrage, reiterated her knowledge of his sins, and then, fearing she would not be believed, hurried away.
Don Juan, glad to escape, followed her by another path, saying that he wished to see she did herself no harm; and when he had gone, Donna Anna, who had been watching him constantly, declared to her betrothed that she now knew it was Don Juan who had been her would-be ravisher, and the murderer of her beloved father, since his agitated voice and angry gestures when disturbed by Elvira had betrayed him.
Full of horror that they had thus unwittingly sought help from the very villain they wished to punish, the lovers hurried after the retreating Elvira, whom they soon overtook; and after having listened to the sad story she had to tell of herself, the three determined to bring retribution on Don Juan, and to begin their scheme by exposing him as a villain before his own assembled guests that night. Having returned to the inn, they disguised themselves in long black dominoes and half-masks; and then when darkness fell they made their way back to the palace grounds, where they were soon seen by Leporello and invited to enter the great hall.
Meanwhile, the sly Leporello had also enticed back the timid Zerlina to the revels, and more than once Don Juan had tried to draw her away with him. But the rustic lover, Masetto, was jealous and suspicious of the great lord's attentions to his pretty sweetheart; and several times during the afternoon he had lain in wait behind bushes and stepped out in time to prevent a stolen interview. Zerlina tried to soothe him with her pretty coaxing ways, feeling that her high-born cavalier merely admired her, and meant her no harm; but later on she was undeceived.
The revels were to end in a masked ball at night, and as soon as darkness fell, the delighted peasants, all decked in dominoes and masks, trooped gaily into the palace once more, to dance and feast in the banquet-hall.
Don Juan, gorgeously attired, moved authoritatively about the gilded salons, ordering every kind of comfort and delight for his lively guests; but all the while he kept a watchful eye upon the pretty Zerlina, determined to gratify his sudden passion for her that evening. At last his opportunity occurred; and having bidden Leporello keep Masetto occupied for a short time, he secured Zerlina for a partner in the dance, and in its mazy movements sought to draw her into a private inner room.
Donna Anna and her two companions watched this manœuvre with anger in their hearts; and when Don Juan's fell purpose presently became patent to all, they pulled off their masks and denounced him before his own guests as a base villain, relating the many evil things they knew of him.
Masetto, now roused to fury, rushed boldly forward to attack his enemy, calling on his friends to help him; but Don Juan quickly drew his sword, and clearing a way for himself, managed to make his escape.
Seeing that their prey had slipped through their grasp once more, Donna Anna and her betrothed returned to the city; and shortly afterwards Elvira also took up her abode in Seville, hiring a house, and taking Zerlina with her as her maid.