The subplot of this play concerns the two characters of Peregrine and the rather naive and foolish Sir Politic Would-Be. The key events in the subplot are the ways in which Sir Politic tries to present himself as an experienced traveller with an intimate knowledge of Venice, where the play is set. He also shares his ludicrous schemes for making money. Peregrine, rather more streetwise, sees through the pomp and vanity of Sir Politic Would-Be and determines to trick him for his own amusement.
There is a definite parallel in terms of theme and plot between the main plot of Volpone and his avarice and how this leads him to trick the various suitors who gather round his supposedly dying body and the way in which Peregrine fools Sir Politic Would-Be. Both Volpone and Peregrine show themselves to be very canny and intelligent individuals who are able to identify and use the weaknesses of others against them for their own benefit. The only difference would be that the kind of revenge that Peregrine visits upon the poor Sir Politic is far more ridiculous than what Volpone does to the suitors. Making Sir Politic crawl across the floor pretendign to be a tortoise hurts only his pride and exposes him for the vain, pompous fool that he is.
What connects the two is the way that Venice is presented as a world made up of deceivers and the deceived. Jonson through the subplot and the example of poor Sir Politic seems to suggest that it is only a very brave or/and foolish Englishman who would enter such a brutal environment.