You can find that out right here on eNotes.
Volpone is a rich and miserly man, kind of like Scrooge. The basic plot revolves around competition to become Volpone's heir. Volpone is pretending to be dying and trying to decide upon who his heirs will be. Several people visit him in the hopes of getting named heir. Volpone's secretary, Mosca, tries to make each visitor think that they are the ones that have been named the heir, even though none of them has been.
Volpone is deceiving them, but in turn, the other characters try to deceive Volpone (in a very complicated plot involving disguises, subterfuge, etc.). One of the main themes, therefore, is greed. Everyone is trying to position themselves to receive Volpone's money. But Volpone is not to be trusted, so another theme is deception. The play ends with almost everyone's downfall, so it is a morality play - greed and dishonesty do not pay.