In Antonio Saracino's Rome, his day starts on a sour note as he discovers that his new Fiat 1100 has been stolen during the night. Next, the commissioner goes to the customs inspector Mastrillo in connection with a box of medicines stuck in customs. However, Mastrillo is inflexible and does not grant favours to the commissioner. Saracino then goes to a women's lingerie shop to procure disguises for himself and Brigadier Di Sabato, but discovers that the shop is run by Inspector Mastrillo himself, who uses this contrived strategy to circumvent restrictions on his civil service position.
During the meeting, Mastrillo confesses to having swindled the customs administration out of more than a billion lire and proposes to Saracino to join his scheme. However, Saracino feigns interest and secretly records the entire conversation with a hidden microphone before having Mastrillo arrested.
Cavalier Alfredo Fiore, relying on the 'revelations' of his parrot, accuses his wife of cheating with the vet, Dr. Cavallo, and asks for police intervention. The commissioner, however, dismisses him out of hand. Later, Cavalier Fiore returns, claiming to have been the subject of an attempted poisoning, but is again turned away by the commissioner.
Colonel La Matta, who introduces himself as a private detective, informs Saracino of an isolated villa where many girls enter every day without leaving. Saracino and La Matta pretend to be painters to investigate and discover that a horror film is actually being shot. Next, nurses from an asylum arrive and take La Matta away, who is actually an escaped patient from the asylum.
The last case concerns Commendatore Lancetti, the victim of blackmail by a mysterious man. Saracino suspects there is more going on than meets the eye and suggests to the commendatore that he pretend to agree with the blackmailer and meet him at Villa Borghese. There, disguised as a prostitute, Saracino discovers that the blackmailer is the commendatore's brother-in-law. However, he also discovers that the commendatore is involved in forgery, as he is carrying counterfeit banknotes. Consequently, Saracino arrests both of them.
After the arrest, a police officer warns Saracino that his car has been found. It turns out that the car was stolen by a gang of thieves that Don Amilcare, a priest, tries to redeem on one side and protect on the other. Don Amilcare is in the car with one of the thieves named Pecorino and is returning the car to its rightful owner. Initially, Saracino suspects that Don Amilcare is an accomplice of the thieves, but when the priest returns the car, he changes his mind and is convinced of his innocence. However, Pecorino, after promising to stop stealing, decides to commit one last heist when he discovers Don Amilcare and Saracino in the car. The latter is still pretending to be a woman and feels slightly ill. Don Amilcare decides to take him to a doctor, but Pecorino, mistakenly convinced that the priest has succumbed to female temptation, decides to continue his criminal career.