A small time delinquent, turned police mechanic for a go fast task force, is forced to defend his innocence when his mentor is killed by dirty cops.

The officer Nico Giraldi investigates a homicide which has taken place in a Chinese restaurant in Rome. His wife and his son are kidnappeded by the murderer in the course of the inquiry. In the end the case is worked out.

A police inspector is called to Milan to investigate a murder case since he grew up in the same ghetto as the suspect.

Now an agent of Interpol undercover, the former Inspector Giraldi, goes to New York to find his friend Salvatore Esposito, aspiring restaurateur in Little Italy, suffocated by debts with the usurers headed by Don Gerolamo. He will remove the gang and assure her of justice, but she will suffer the advances of the Boss's daughter, the ugly Maria Sole.

This time the "amici" (friends) are just four: Necchi, Meandri, Mascetti and Sassaroli. Nevertheless they are older they still love to spend their time mainly organizing irresistible jokes to everyone in every kind of situation. Mascetti is hospitalized in a geriatric clinic. Of course the place become immediately the main stage for all their jokes. After some jokes they decided to place an ultimate incredible and farcical joke to the clinic guests.

While keeping an eye on his small time crook brother in law, Inspector Nico Giraldi gets involved in a murder case set in the world of Formula One racing. Giraldi is suspended for trying to cover up for his brother in law and becomes afraid his wife and son may be targeted next. Therefore he calls in the help of his childhood friend and chief informant, Venticello.