Filippo Ferrari and Carmine Di Salvo come from two different backgrounds. The first is from Milan, wealthy and a talented pianist. The second is Neapolitan and belongs to a family of the "system" but, unlike his parents, he has chosen an honest job and his dream is to be a hairdresser. But fate has decided to trip both of them up: Filippo and Carmine find themselves sharing the same cell in a juvenile detention centre in Naples. Filippo, after a night of MDMA at the disco with his friends, finds himself on top of a tower to challenge his best friend in a test of courage. Unfortunately the challenge ends in tragedy and Filippo is accused of murder. Carmine, on the other hand, when one of the boys from the rival clan tries to rape his girlfriend, kills him with hairdresser's scissors.

Carmine and Filippo enter the Juvenile Detention Institute. Carmine knows the rules, while Filippo seems to have landed on another planet. He is immediately nicknamed 'o Chiattillo (The Young Master) by the other boys. Ciro, the boss of the convicts, seems intrigued by Chiattillo and in exchange for his services offers him his protection. Meanwhile, Carmine is brutally beaten up by one of Ciro's henchmen, Pino. Commander Massimo doesn't seem to worry too much: when new elements join a group - already complex in itself - there are always aftershocks. It's in these moments that you have to be vigilant without intervening. The headmistress, Paola Vinci, is not of the same opinion and punishes the boys. Filippo, convinced that the magistrate is about to put him under house arrest, refuses Ciro's protection and does not follow his orders. In response, Filippo is subjected to yet another humiliation at the canteen and reacts by offending Ciro and his henchmen.

A new character enters the prison: Naditza, a regular at WM. Nad has herself arrested to escape the fate her family has decided for her: to marry her in exchange for money to a cousin twenty years her senior. Nad plays the piano like Filippo and makes a bet with the other inmates: within a few days the Chiattillo will drool at her feet. Ciro can't wait to avenge the death of Nazzario Valletta, killed by Carmine, who feels the noose around his neck: everything he wanted to get away from has come true, he is now a prisoner with a death threat on his head. Filippo in prison awkwardly tries to catch up with Ciro and his affiliates, boasting of being there for having committed a crime of honour by killing an infamous man, but when Pino 'O Pazzo discovers that the Chiattillo told a lie for him things get bad.

The spotlight is on Viola, an icy girl serving a sentence for murder with the aggravating circumstance of cruelty. The girl is charismatic and Ciro himself suffers from her magnetic charm. Naditza comes into conflict with her and tries to free other inmates from her "yoke". Matron Paola has a new project for the WM: to have the boys participate in recreational activities together with the girls. Commander Massimo is against it while Beppe proposes a music course: Naditza can play but has never studied, Cardiotrap can sing but doesn't know music, Filippo could be a teacher. The first lesson does not go as hoped. To appease Pino's aggression towards him, Filippo does the last thing he should do: he buys him a present. Pino thanks him, but soon the others demand the same treatment and when their requests are not met, trouble begins.

Gemma, a girl from Rimini, habitually suffers violence from her boyfriend, but when her sister becomes a victim herself in order to defend her, revenge seems to Gemma to be the only way to heal her sick love. Revenge is also what Filippo is meditating on, as he won't resign himself to the abuse Pino is subjecting him to. Now he has a weapon and has every intention of using it in his defence. Carmine, on the other hand, has been reborn after hearing the news that he is soon to be a father. He cannot lose hope because he has a reason to fight. But Carmine is still threatened with revenge by the Vallettas. In the meantime, the headmistress is informed of the disappearance of the razor blade stolen by Filippo and suspends both permits and recreational activities. This fuels anger among the inmates who think Carmine is responsible.

Edoardo goes out on leave. Filippo gives the razor blade to the director, but Paola can't get him to reveal who he was defending himself against. Ciro learns that it was Filippo who stole the razor blade. Pino wants to teach him a lesson, but Ciro seems to have something else in mind for Chiattillo. Filippo takes Ciro's bait and accepts his protection. Carmine warns him: the friendship that Ciro is offering him is called "belonging" to the "system": one is indebted for every favour received. Carmine is right and in fact Ciro asks Filippo for a test of courage to obtain his protection. In the meantime Gemma enters the feminine world and Viola starts to manipulate her with her manipulative art...

The friendship between Filippo and Carmine is in crisis just when they need each other. Filippo is not long in discovering the price of Ciro's protection: during his leave he will meet his family in a restaurant. Edoardo takes advantage of the activity at the pottery workshop to court Teresa in his own way. Gemma, during her conversations with her mother, discovers her sister's deterioration and sinks into a state of guilt; Viola, meanwhile, sensing her weakness, keeps circling around her.

Massimo continues to keep a close eye on Carmine and suspects nothing of the order he has received. He sees himself in him, tells him his story, how sometimes it is difficult to make the right choice because it involves a very high price to pay. Meanwhile Filippo has met his parents in Naples, he has to obey Ciro and put his father's car at the disposal of the young boss' friends.

Filippo returns to the Institute after completing his operation and tries to get closer to Carmine. Edoardo writes a beautiful poem inspired by Teresa, to try to take part in a competition and obtain a permit award. Viola is able to manoeuvre Gemma and pushes her towards the boyfriend she tried to kill to avenge her sister.