Voltore is pleased to find Mosca taking inventory, but he is suspicious of the gadfly's new garb. For his part, Mosca completely ignores the vulture and his questions. Old Corbaccio comes on the scene with the same questions Voltore has, and Mosca continues to devote his entire attention to the inventory. Finally, Corvino rushes in to ask Mosca if the hour has come.
Volpone peeps out from behind the curtain to have a better look at his joke and is almost discovered when Lady Would-be appears unexpectedly. Corvino asks the counting Mosca for the will, and without missing an item or a beat, Mosca hands it to him. The others gather around to see their fortunes made; Mosca remains preoccupied with his work. Suddenly, the gulls scream their discovery: "Mosca the heir!" Voltore is stunned, and Corbaccio snatches the will from Corvino, who rushes to Mosca demanding, "Is this in earnest?"
Mosca continues his infuriating count, pausing to say only that he is very busy: "Good faith, it is a fortune thrown upon me . . . not my seeking." Finally, Lady Would-be demands a direct answer. Mosca's reply is brutal: "Remember what your ladyship offered me to put you in an heir." Undone, Lady Would-be flees from the scene of her compromise. Volpone is pleased at this beginning.
Corvino is the next gull to press his case. Mosca shows him the valuable gifts that Corvino gave to Volpone and that now belong to the gadfly. Mosca is duly grateful for the raven's generosity. Nonetheless, Corvino's greatest gift, his wife, though not a part of the inheritance, makes him a cuckold. Mosca will not betray him; Corvino leaves in frustrated anger. "Rare, Mosca!" says the hidden Volpone. "How his villainy becomes him!"
Voltore's hopes rise as each of the other gulls leaves with empty hands. Suddenly, Corbaccio shouts, "Mosca the heir?" Volpone collapses with laughter, saying "Oh, his four eyes have found it!" Impotent Corbaccio screams epithets at Mosca; the gadfly replies: "Stop your mouth, or I shall draw the only tooth [that] is left." Mosca accuses Corbaccio of the covetous greed that caused him to disinherit his son. The old crow stumbles blindly from the scene.
"Now, my faithful Mosca," begins the vulture, but Mosca's mood remains constant. Mosca flatters Voltore's talent for pleading in court, and the gadfly trusts that the vulture will prosper while there are men, and malice, to breed causes. As a matter of fact, Mosca, if the need arises, will hire Voltore's talents at a fee. Mosca applies the finishing touch by thanking Voltore for the gold plate he gave Volpone. Voltore's humiliation is complete.
Volpone comes out of his hiding place and showers praise on his parasite. If only he could disguise himself and follow the gulls, he could further enjoy his triumph. Mosca readily agrees to fit his master in a rare disguise. The disguise is an outfit of a commandadore, or police officer. Mosca tells Volpone to look for curses. Volpone replies that "the fox fares ever best when he is curst."
Mosca begins this sequence with an air of preoccupation. It is the complete reversal of roles that makes this scene so hilarious. The gadfly has lived on the leavings from Volpone's victims; now it is Mosca's turn to be courted. They have come to Volpone's house to hover over his dead body. They have been fooled; there is no body. Instead, they have a wily heir to cope with.
Mosca is a formidable personage to these greedy gulls because he knows the crimes their greed has led them to commit. At first, Mosca toys with them. The stage business is particularly funny during the early part of the scene. Mosca's motion is deliberate and the gulls' movements are agitated. Volpone begins the extensive asides employed by the playwright in Act V. These require good timing and a fine sense of the distinction between talking in character to another character and talking confidentially to an audience. During one of the asides, Volpone is nearly discovered upon the unexpected arrival of Lady Would-be. It is the kind of hairbreadth escape that audiences delight in.
In spite of the continued fun, this is a difficult scene for the actor playing Mosca. He must make the transition from a man of pure license, a prince of folly, to a very greedy fool. Jonson accomplishes the transition in the script by suddenly dispensing with the use of hyperbole. Now everyone says exactly what he means. In the hands of an inexperienced actor, the change to a new game will seem harsh and cruel. There is little gaiety in cruelty. It must be remembered, however, that Mosca merely tells the gulls that they have been foiled by their own foolishness. It is a true comic punishment. The avocatori and the Venetian court have failed to perceive the iniquity of these villains. Only a fool can bring them to justice. This savage irony is accompanied by Volpone's delight in Mosca's newfound cruelty.
It is Volpone's need for more and more cozening that puts into Mosca's hands a weapon that will bring the whole business down on their heads. The intrigue of the will causes Mosca and Volpone to fall out. As long as their solidarity is unquestioned, these two rogues must prevail. As soon as Mosca has a legal chance to become Volpone's equal, they become adversaries rather than cohorts. But Volpone is slow to understand the situation, and this is what brings about his destruction. Rare Mosca's becoming villainy is delightful when it is used on the gulls. It is ironic that the price of observing and enjoying that villainy is Volpone's own undoing.
Mosca sends the gulls away by reciting their sins to them. The generous way he assures them that he will not reveal their secret to the courts is infuriating. They cannot prosecute him to get the money they desire. The galling part is that, only yesterday, Mosca was a lowly, fawning servant.
Mosca is still a master of human nature. His ironic promise to employ the lawyer's talents for a fee displays his understanding of Voltore. These insults and dismissals at the hands of a parasite and a servant who is beyond the pale of justice are the real comic punishments the playwright has prepared for his foolish gulls. It cannot be the only punishment, for these birds have caused innocent people to suffer. We must go back to the courtroom because Celia and Bonario are to be sentenced there.
Before we get to the courtroom, Volpone's insatiable desire for trickery must set up his ruin. So it is that Mosca agrees to fit his master with a new disguise. It is again ironic that Volpone should dress up as a policeman. It is this disguise that will lead to his apprehension.