Voltore, Corbaccio, Corvino, and Mosca prepare to go before a court of law. Voltore says they’ve figured out how to manage the situation with Celia and Bonario, and Mosca confirms that they have all agreed on the lie they are going to tell. Speaking aside, Corvino makes sure that Voltore does not know the truth of the matter, and Mosca says that he made up a story to preserve Corvino’s honor. Corvino is afraid that Voltore’s speech in court will make him a co-heir, but Mosca says they’re just using Voltore for his speaking ability.
Voltore, Corbaccio, and Corvino have now all been co-opted into one of Mosca’s dramatic fictions. That this will be a court drama underscores the play’s theme of appearance and reality; all have agreed on the lie to tell in a venue dedicated to finding the truth. After seeming shameless when offering Celia to Volpone, Corvino is now concerned about his public image and the honor he said did not exist, reasserting the importance of appearance over reality for the corrupt characters.
In an aside to Voltore, Mosca makes fun of Corvino for being a cuckold. Then to Corbaccio, Mosca says that only Corbaccio will receive the fortune, and that the other men don’t know for whom Mosca is really working. Mosca keeps whispering asides to himself and to all three men, convincing them all he is on their side. Just before the court session is about to begin, Mosca tells Voltore that he has another witness if needed.
Mosca revels in his ability to simultaneously fool all three men, even when they are together in the same room. This arrogance lays the groundwork for his downfall. The extra witness Mosca refers to is Lady Would-be, who believes Celia is the prostitute Mosca pretended he saw with Sir Politic.