Mosca enters, bleeding from a sword-wound that Bonario has given him on his way out. Volpone is concerned by the injury, but when Mosca blames himself for the disaster of Celia's escape and Bonario's discovery of Volpone's deceit, Volpone readily agrees. They briefly consider what they are going to do, with Mosca suggesting suicide. Then they hear a knock at the door; it is Corbaccio.
Corbaccio enters, with Voltore following right behind. Mosca tells Corbaccio that his son was searching to kill him, in revenge for his disinheritance. Corbaccio accepts the lie readily and agrees to make Volpone his heir, asking Voltore if Volpone is going to die anytime soon so that he can inherit his money. Hearing this, Voltore becomes angry and accuses Mosca of double-dealing; who is going to be the heir, he demands, Voltore or Corbaccio? Mosca professes his loyalty to Voltore and then recounts the events that have just happened with a deceitful spin. Mosca tells Voltore that he had brought Bonario in to watch his father sign away his inheritance to Volpone, in the hopes that the enraged Bonario would kill his treacherous father, thus leaving the path open for Voltore to inherit the magnifico's wealth. But, lies Mosca, Bonario grew impatient waiting for his father, thus kidnapped Celia and made her "cry rape," in order to frame Volpone and thus make it impossible for him to inherit. Voltore, ever the lawyer, immediately takes Mosca's side, seeing the threat to his own interests (if Volpone is convicted he will not be able to inherit anything, or pass on an inheritance), and he immediately demands that Mosca fetch Corvino and bring him to the Scrutineo.
When Volpone loses control with Celia, he breaks the implicit rules he seemed to be playing by initially, or at least may have fooled the audience into thinking he was playing by: that he was only out to deceive and hurt those who deceived and hurt themselves. But this has now been shown to be false, the audience has shown itself to be "gulled" (fooled) by Volpone, and so we are now much less likely to take his side. Our loss of sympathy for Volpone and his loss of control over the situation lead to what can be termed as the "disestablishing" of Volpone as the play's protagonist: he is no longer is the hero, or even the anti-hero, of the play, which he has been since the first scene. From his perspective within the play, he is no longer in control over his own life. Instead, the increasingly independent Mosca becomes a substitute protagonist, and Mosca's "sidekick" role is assumed by Voltore. In Act V, Volpone seems to regain control over his life (and his role as protagonist), but this leads to a destructive confrontation between him and Mosca. The didactic element of Volpone becomes pronounced here (an artwork is didactic if it aims to teach or educate). Jonson teaches us in this scene never to trust someone like Volpone, an energetic person with a gift for deceit, and he will attempt to show that, in the end, people like Volpone are always done in, usually by their own decision to trust someone.