Antonio Bonocore, caretaker of a building in Rome with a German wife, is to attend the passing of Mr. Andrea, an elderly tenant who, before dying, tells him to be in possession of a suitcase inside with a few original clichés of the Bank of Italy, of which he had long been an employee, and the watermarked paper to print the 10,000 liras banknote. Mr. Andrea had stolen this material with the intention of "revenge" of his retirement and make fake money. But he never had the courage to succeed in its intention and, therefore, asked Bonocore to throw the bag into the river to destroy the contents. Bonocore, however, is going through a bad time: basically an honest person, has refused to become an accomplice of accountant Casoria, the new administrator of the condominium, which had proposed to make a series of fraudulent transactions against the same building, and for this reason is under threat of dismissal. Thus he decides not to destroy the bag but, ignoring the banknote printing techniques, to produce 10,000 notes is forced to ask the cooperation of the typographer Giuseppe Lo Turco and, later, the painter Cardone, both with economic problems. Building on the economic needs of his cronies, Bonocore arranges secret and hilarious meetings at night to give life to a gang of counterfeiters. The three manage to print banknotes and "split" in a tobacconist one night, but things get complicated when Bonocore discovers that his eldest son Michele, a brilliant revenue officer recently moved to Rome, is following its own delicate investigation on a batch of counterfeit notes. After having heard some details from Michele, and vaguely talked to the supervisor of his son, Bonocore came to visit him at home. Seeing the finance police searching for Mr Lo Turco and noticing strange changes in style in his "partners", Antonio is afraid of being discovered, with the aggravating circumstance that all of this, since he is the father of a revenue officer, would cost the job to his son. So he begs his cronies do not spend a lira and immediately dispose of the equipment, burying it out of town. The son, seeing this strange burial by chance, asks his father what he is doing, but Cardone, also present, does not think better than to say they are burying Mustafa, Bonocore's poodle, killed by a car. Antonio is therefore forced to get rid of the dog, and not having the courage to kill him, leave him on the road, tied to a milestone. But Mustafa freed itself and returned home during a visit of Michele's supervisor, when he notices it in embarrassment. Antonio, now feeling hunted, matures the idea, which he expresses to Lo Turco, to get arrested by Michele: a son who arrests his father - he says - not only will not be sacked, but also would be promoted and would become an example for all of his colleagues. Therefore, he decides to implement his plan by going in person to the police station to be arrested by his son, who thinks his father is just joking. But, after hearing by Michele's supervisor that the investigation followed by Michele resulted in the arrest of professional counterfeiters. And when the supervisor says the note identified by the police was not one of those produced by the three, but the sample used - a false note supplied by a money lender, Bonocore is about to faint. At the end it turns out that none of his members had had the courage to spend the counterfeit notes. The three, now at peace with themselves, decide to destroy all counterfeit notes and the suitcase with the clichés, setting up a bonfire: as a final gag, Bonocore realises that he threw into the flames, in the hurry, even the envelope containing his salary.
