Gaetano and Roberta go through a story made of everyday life and tension, in which arguments and reconciliations follow one another. Meanwhile Camilla discusses with Anna the suspicion that Quantunque might be involved in shady business.

The world of research can also be told with lightness and self-irony: through traditions like an annual play, scientists transform discoveries and great protagonists into opportunities for joking and sharing, revealing the more human and fun side of theoretical physics.

The investigation into Lara's death continues, while the police conclude the interrogation of the suspect. Meanwhile Aragona, in order to go out with Irina, promises her that he will find the culprit.

Rosario and his mother share a secret and touching moment in the school that the boy attends, between music and complicity. At Matteo's house, instead, tensions emerge between uncle and nephew, fueled by emotional conflicts and misunderstandings.

Camilla needs to speak to Anna and phones her, only to find out that Anna had just forced the briefcase open at Quantuque's place. Meanwhile, the investigators interrogate a witness who points to a possible suspect.

Fabiola Gianotti's account retraces a serious technical incident that affects a major scientific experiment, the initial shock and the subsequent recovery. In parallel, her personal reflections and the strong emotions linked to the responsibility of leading the project emerge.

The police interrogate Cuocolo after the arrest and he tells of having met Lara on the Mergellina waterfront and of having had a casual relationship with her. However, he denies being the father of the child and claims to have an alibi for the night of the murder, suggesting that the culprit could be someone in love with her who was not reciprocated.

Rosario finally meets his mother during a visit. The two speak with affection, but also with a certain embarrassment about Antonia's difficult past, who however tells him she is feeling better and has reduced her medication. The woman then tries to learn more about her son's life, asking him about school and his friends. Meanwhile, Barbara is scolded by her mother because she is always glued to her phone.

Gaetano and Roberta argue heatedly about the wedding preparations and family responsibilities; the argument angers Roberta, who decides to leave. Meanwhile, Camilla asks Gaetano for help and, thanks to a photograph, a young man is connected to the woman found murdered. For this reason, Gaetano wants to speak with Anna to get more information and deepen the investigation.

Here is the account of the startup of the Large Hadron Collider at CERN on September 10, 2008, when for the first time proton beams began to circulate in the accelerator ring. The event, followed live by the media, is presented as a historic moment for science, despite the fears and catastrophic news spread in those days.

Lojacono pursues and arrests Donato Cuocolo. After attempting to flee and threatening the officers with a brick, he is stopped by Alex Di Nardo. At the police station, the investigators put him under pressure: he risks many years in prison, but he can face a lighter charge if he cooperates.

Marioni is forced to give up conducting the concert due to his injury, while Rosario receives an affectionate visit from his mother, between tenderness and a touch of embarrassment. In a record shop, unexpected confidences emerge and, once again, between music and complicity, the young people confront love and friendship.

Camilla finds herself involved in the difficult situation of one of her former students, obsessed with Quantunque, who has mysteriously disappeared and whom she wants to help at any cost. Between enigmatic messages and a photograph that has resurfaced from the past, the investigations proceed amid suspicions and uncertainties, without yet a real breakthrough.

In this part Fabiola Gianotti talks about the connection between science and creativity, combining physics and music as universal forms of expression. She also explains the work of the Large Hadron Collider, where proton beams are made to collide to study the universe right after the Big Bang.

While Romano talks with the doctor, he meets Giorgia at the hospital, who is there to assist her hospitalized mother. Meanwhile, at the police station, new clues emerge about a suspect linked to a criminal clan, while Laura and Giuseppe share moments of complicity that lighten the tension of the investigation.