Volpone confesses to Mosca that cozening the court in such a grand manner was worth "more than if I had enjoyed the wench." Mosca is content to let the whole plot rest: "This is our masterpiece; we cannot think to go beyond this." Volpone's praise of Mosca is unstinting, and the two fall to laughing at their late triumph over the court and the innocents. Volpone imitates Voltore's speech to the court; the language and voice are perfect. Mosca asks Volpone if he did not sweat a little. "In troth," says the fox, "I did a little." Voltore made such a great effort on their behalf that he should be very richly cozened. The two rogues are working up gales of laughter; they have all but lost control of themselves. Finally, Volpone promises to vex all of the gulls from this instant. Clapping his hands, Volpone summons his fools. Would they enjoy some farcical entertainment? Then go out into the streets saying that Volpone is dead! They must do it sadly and "impute it to the grief of this late slander." Mosca shall be his reputed heir. Taking a blank sheet of paper, Volpone fixes his name to his last will and testament.
Volpone develops the new plot in the following manner. Mosca is to put on an expensive gown, take up pen and ink, and begin taking an inventory of Volpone's hoard. If anyone should ask after Volpone's body, the fools are to say it was corrupted. Volpone will "get up behind the curtain, on a stool," and watch the circus unfold. While anticipating the reaction of the gulls to this new cozening, the two rogues begin dressing Mosca and arranging Volpone's hiding place. Suddenly, someone is knocking at the door. It is the vulture. The villains get into character for their charade, with Volpone encouraging Mosca to "torture 'em rarely."
As the scene begins, Mosca and Volpone repeat their triumph and its satisfaction. Jonson points out Volpone's principal deformity: It is cozening, not merely wealth and wenching, that he enjoys. Volpone did desire Celia, but he enjoyed cuckolding her husband as much and cozening the court more than he would have enjoyed possessing Celia. This is of primary importance in relation to the play's conclusion.
The two dissemblers slowly build their mirth until, under its heady influence, Volpone is induced to throw caution to the winds. Jonson provides his actors with a chance to mimic other actors and the opportunity to envelop the audience with their infectious laughter. They must be irresistible rogues.
Almost spontaneously, Volpone succumbs to his greed for cozening. He improvises his own death to bring out the attending greed of the birds of prey. Then, with inspired irony, he imputes that feigned death to the late slander to his good name made in the courts of Venice. Mosca seems unenthusiastic for the moment. He had used all of his cunning to extricate himself from the last close call. Nonetheless, Volpone's spirits have returned, and his invention with them. The inspiration of Volpone's last will and testament changes the whole complexion of the play. Mosca's eyes must begin to regain their roguish glint; his person must seem more determined than lighthearted about the trickery, for this act puts Volpone within Mosca's power and causes his downfall. It also brings out Mosca's humanity.
Until that moment, Mosca was a parasite and was therefore outside the temptations of normal society. Once he is willed the money, he sees his first chance to come up in the world on his own. For the first time, Mosca performs his tricks not for their own sake or his master's gain but for his own material advancement. Until now, Mosca has not been subject to greed, the main vice of the play. Greed has succeeded in making men foolish; it will surely do the same to Mosca. So long as he was without ambition, Mosca was superior to his fellow men. He must know that ambition will make him a fool like the others, but he cannot resist the temptation.