Peregrine enters, in disguise as a merchant. He is accompanied by three other merchants. They rehearse a scheme in which Peregrine has hatched to get his revenge on Sir Politic; Peregrine reminds everyone that his only aim is to frighten Sir Pol, not to injure him. The merchants hide, and Peregrine puts his plot into motion. Peregrine asks Sir Pol's serving-woman to tell the knight that "a merchant, upon urgent business." When Sir Pol comes out of his study, where he has been working on a letter of apology to his wife, Peregrine's disguise is successful; Sir Pol does not know he is talking to Peregrine. So Peregrine/the Merchant tells Sir Politic that the young man Sir Pol was speaking to earlier that day (that is, Peregrine) has told the State of Venice that Sir Pol wishes to sell Venice to the Turks. Sir Pol believes Peregrine immediately, and becomes terrified. After all, he did tell Peregrine he could sell Venice to the Turks; of course, he had been joking, but now it seems that Peregrine has understood things in a very wrong, and dangerous, way. Of course, Peregrine has told no such thing to anyone; but when the merchants knock on the door, Peregrine/the merchant tells Sir Pol it is the officers of the state come to arrest him.
Sir Pol decides, at Peregrine's suggestion, that he will hide in a wine cask made of tortoise-shell; he quickly does so and asks Peregrine to tell his servant that his papers should be burnt. When the merchants come in, they walk around the room; Peregrine "informs" them that he is a merchant, come to look upon a tortoise (actually Sir Pol hidden in a wine cask). The merchants express awe at the tortoise, and Peregrine/the Merchant tells them that the tortoise is strong enough for them to jump on. So they do. They then ask if the tortoise can move, and Peregrine informs them yes. So the tortoise does, and they remark that the tortoise has garters and gloves on. Pulling off the tortoise shell, they reveal Sir Politic. After laughing at his expense, Peregrine claims that he and Sir Politic are even, and apologizes for the burning of the knight's papers that resulted from the joke. The merchants and Peregrine all leave Sir Politic to wallow in his own humiliation and self-pity. The abused Englishman asks his servant where Lady Politic is; she tells him that she has decided that she wishes to return home, for her health. Sir Politic whole-heartedly concurs with his wife's plans..
Peregrine's final scene with Sir Politic is in one sense pure farce, intended to make us laugh. But it also foreshadows more serious events about to occur in the play's main plot, events central to the play's moral satire and didactic purpose. Sir Politic disguises himself in front of the Mercatori, just as Volpone will disguise himself in front of the Avocatori during the final scene. Politic's "unveiling" to the Mercatori will be echoed in Volpone's own unveiling. And both characters are the victims of an ironic reversal of fortune; whereas Volpone is disinherited by the same trickery he used to disinherit others, Politic will now become "talk for ordinaries," the butt of one of the many gossipy tales he himself is so fond of telling. Whereas Volpone disguises himself as a commandadore, Politic disguises himself as a tortoise; as we know Jonson likes to identify characters with animals, the choice of tortoise here seems particularly apt, being a slow, dim-witted animal, not nearly as attractive as a Fox. And whereas Volpone will manage a Pyrrhic victory by exposing Mosca's deception, Politic is merely jumped upon and abused by the Mercatori. Peregrine plays a parallel role to Mosca in the subplot, turning Sir Politic's machinations against himself; but Peregrine is portrayed sympathetically. Whereas Mosca is eventually shamed in front of the Mercatori, and made to pay the harshest punishment than that handed out to Volpone. Politic's situation is a farce, however, both because of the complete loss of dignity and humiliation to which he is subjected, and the fact that this loss of dignity is not in any real way harmful. But this is appropriate; in fact, if it results in him leaving Venice, it may very well be beneficial for him. Volpone's will not be so lucky; Jonson's satire will be much more harsh with him, his tone more severe. We can see that this is appropriate; Sir Politic has not, in fact, done harm to anyone, whereas Volpone has endangered the lives of two innocent people.
This scene also identifies Politic's place within the beast-fable that has been an undertone throughout the play. If we remember from Act One, we have a Fox (Volpone), circled by a Fly (Mosca), and three carrion birds7—the vulture (Voltore), the crow (Corvino) and the raven (Corbaccio). Politic, on the other hand, is a tortoise: a slow, dim-witted animal who carries its house on its back. Similarly, Politic is dim-witted, slow and English, no matter how hard he tries to be Venetian. He is thus a symbol of someone out of his element; amongst the cunning and carnivorous creatures of the main plot, the tortoise is no match, and will eventually retreat back into its shell, as Sir Politic seems ready to do at the end of the play. Thus, though Sir Politic is an object of fun, he is also an object of sympathy, especially for the English audiences of the play. Contrast this to the treatment the Venetians Volpone and Mosca will receive, and we begin to suspect that Sir Politic's "English-ness" gives him a preferential status; as the character the audience probably identifies most closely with (by virtue of his nationality), he is portrayed as something of an innocent; it is the foreigners who are viewed as intentionally evil, and worthy of punishment.