Pietro, a pediatrician, widowed for years, lives for his profession in the bright San Pietro Island. Someday his daughter Elena, a young policewoman, reappears in his life. After fifteen years of absence, the woman stays in Carloforte to investigate the collapse of a tuna factory that killed few young and doesn’t seem to be an accident. Who would kill a group of eighteen years old kids? By her side during investigation, Alessandro, the first love -and also vice police commissioner of the island- she had to abandon for a unmentionable secret… Because she is the unknown mother of Caterina, a girl unaware of the true identity of her mother and who lived in Carloforte for fifteen years with a friend of Sereni’s family. And now Caterina seems to be guilty of the explosion and about to do something desperate

Elena and Pietro can take Caterina back home. The girl is pregnant of her classmate Fabrizio and talking with Elena, she promises to tell her parent, Grazia and Enrico, everything. This attention to the girl leads Pietro to the right track… and make him discover the truth: Caterina is his niece. Interrogated by the police, the girl confesses that at the party there was lot of drogue. Police investigation then shift on a pushing drogue track. Alessandro is worried about his brother Samuele to be involved, because he had a drogue addiction when he was younger, but Elena hopes for his involvement. Samuele raped her fifteen years ago, and after this violence Caterina was born. Elena fights harshly with Alessandro, even if she doesn’t want to tell him this truth. She loses. Samuele doesn’t have anything to do with the drogue dialing. Maybe there’s another line… someone doesn’t want that Diana awakes from the coma: she’s one of the girls that survived the tuna factory explosion. Why? In the meanwhile, Caterina goes to Pietro’s house. She doesn’t have the slightest intention to go home

Diana, the girl in the coma, awakes. She says she doesn’t remember the last two years because of the trauma. The truth is that a man in the hospital is intimidating her… Caterina is newly under suspicion. Elena finds out that the girl is hiding something, maybe because she is scared too, then the investigation address to Caterina windsurf instructor, who tried to seduce her. Could he be the father of Caterina’s baby? After a harsh interrogation Caterina buckles and admits that her instructor doesn’t know anything and also that she’s not pregnant. Fabrizio thinks she’s fooling with him and breaks with her. In the meanwhile, Elena is forced to tell the truth by Alessandro: Caterina is his daughter. Pietro tries in vain to get closer to his niece Caterina to discover her secrets and if she’s connected to Diana. The doctor sensitivity makes Diana confess that she is faking the loss of memory. She‘s involved in a baby call girl racket. Pietro convince her to tell everything to the police. But before she can do it, Diana is found dead, at the bottom of a cliff

Diana’s dead body is collected from the cliff and the investigation get even more complicated. Elena and Alessandro have very few evidences. Once again, Elena have suspicions, unfortunately, about Caterina. Elena realizes that Caterina is probably involved in the same prostitution racket as also Diana. Tracing the baby call girl organisation line, Alessandro is wounded. Elena has to go on all alone… and has to arrest Caterina: she’s been recognised in the hotel where Diana went to whoring. Pietro is the only one sure that Caterina is innocent. Just when Elena, after her father suggestion, stop being a policewoman and starts being a mother, Caterina decides to confess the awful truth: Diana killer is Enrico, Caterina’s father. He wanted that Diana, his prostitute, didn’t confess his secret. One investigation is ended, suspicions on Caterina are gone but the tuna factory killer is still free. Elena and Alessandro, recovered after the accident, end up making love and finding again a powerful bond. Elena reveal only to him that Caterina is born after a violence… but she can’t tell him who’s the real responsible. In the meanwhile Samuele seems to hide something… may he be the responsible for the tuna factory explosion?

An arson open a new investigation line for Elena and Alessandro: maybe the tuna fish accident is part of a bigger plan of real estate speculation. Elena drift apart from Alessandro, because she’s more and more sure that Samuele is behind the arson. Alessandro is resolute to find out the identity of Elena’s raper. A second arson take Ines’s house, the school principal and dear friend of Pietro. Five years earlier, her daughter Martina drowned after an accident, during a kids sea trip. This tragedy straightened the relationships with Pietro and they became friends. Caterina, with Fabrizio’s help, find out that Grazia is not her mother. Her despair make Pietro and Elena tell their kinship. Caterina reacts angrily and refuses every contact with Elena. In the meanwhile, also with Pietro help, Elena proves Samuele involvement with the arsons. Before the arrest, Elena try to find Alessandro. But he found out that his brother raped Elena and he goes to Samuele’s house to take revenge

Elena and Pietro find Alessandro in his boat, in shock and blood-spattered. Since Samuele has been found dead in his house, Elena fear is confirmed: Alessandro accuse himself for his brother death. Elena is the only one to understands his motivations: he found the truth. And she at last tells her father this truth. Caterina is Samuele’s daughter. During investigation, Elena find out that in Samuele’s house there was another person and she convince herself that Alessandro is innocent. In the meanwhile Pietro examine thoroughly the situation and discover that Grazia lied to fifteen years old Elena about paternity: Caterina is not born after the violence, but she’s Alessandro’s daughter. Before telling this truth to Elena, Pietro must help Elena to solve the case. Together they find out who was in Samuele house: Ines. She killed Samuele because he blackmailed her. He would have forced her to close out her house for his real estate speculation, because he found out that she made the tuna factory explode. Ines discovered that her daughter Martina’s death wasn’t an accident but a terrible classmates joke ended up in tragedy. She arrived by chance at the tuna factory, and opened the gas tanks in a fit of madness, causing the building explosion and kids death. She’s about to put an end to her life, but Pietro save her. Once the case is solved, Alessandro is exonerated and the peace is back, Pietro can at last tell the truth about Caterina and Elena: the family will finally reunite