A quiet Sunday in Rome... for the police officers of the Mobile Squad, however, Sundays, like the rest of the days, are never quiet. This Sunday in particular, everything happens. It would be Ardenzi's birthday but between stalking, drug trafficking and women who want to throw themselves into the Tiber, the day seems to never end.

The Mobile Squad is dealing with a typical day at work in the Capital. An old friend of Ardenzi, a well-known restaurateur in the historic center, turns to the commissioner to solve a problem with his son. Meanwhile, a young girl who is not yet of age is taken to the police station together with the man who lured her.

While at the police station Claudio Sabatini is looking for a way to free Bradic, who is being held awaiting questioning, without arousing the suspicions of his colleagues, Ardenzi and Sandro are dealing with the case of a Pakistani girl stoned to death in the street and Isabella is dealing with her first serious friction with her boyfriend Giulio who ends up slapping her with serious consequences.

Bradic's death at the police station and at the hands of Marcello, forces the commissioner to put the young policeman under investigation and for this reason Oliviero, feeling misunderstood and unjustly accused, runs away and disappears. Ardenzi is worried about the boy, he wants to find him and it is his job to clarify the dynamics of the facts; Claudio Sabatini also needs to find Marcello.

On the day of Valeria's and Zaccardo's wedding, he informs Ardenzi of his transfer to the Viterbo police station. The team therefore has little time to frame Sabatini: they must find the gun that killed Bradic and Clerici as soon as possible and foil the major drug trafficking that Claudio is completing with the help of Vanessa. Sandro finally discovers Sabatini's garage where the gun is kept, but this discovery could be very dangerous.

Sandro, seriously injured by Vanessa, is taken to the hospital in serious condition. Ardenzi recovers Sabatini's gun and can finally prove his guilt. Claudio, now hunted, wants to carry out the last drug trafficking and then flee abroad.