The rich Gaudenzio has promised his ward Sofia to the son of his friend Bruschino without asking. But the latter is held in an inn with a drinking debt. Florville, Sofia's lover, unceremoniously poses as Bruschino junior. The identity theft leads to an absurd situation, because the whole world assumes that old Bruschino is denying his paternity - that is until, in the greatest confusion, the prodigal son turns up.