Two young kids, Henning and Philip are attracted to each other. One night, when they exchange their first kiss, the two boys witness a bloody execution. Narrowly escaping the murderer who just killed four people, they flee with the murder weapon and threw it in the lake. The investigation falls to the adoptive mother of Philip, Helen, a former officer of the Criminal Brigade.
In Oslo, a bomb devastated a restaurant run by Hamit Milonkovic, a gang member of the Z. Her daughter Zana, locked up by him in the building during the explosion, managed to escape. Via Internet chat, the girl comes into contact with the killer of the sandpit. In the forest, Henning realizes that the murder weapon is visible at the bottom of the water hole where he threw it.
Someone tries to kill a motorcycle gang member near a school. A girl is killed. Crushed by the weight of secrecy, Henning does not sleep and becomes violent. Philip confesses to his mom what he had seen. In the criminal brigade, Helen and his team welcome a new chief of investigation a rather intriguing man.
Helen sees her investigation forward significantly: it now has a witness, Henning, who, moreover, gives her the murder weapon. Fearing for his safety, she asked Ron to place the kid under judicial protection. Later, while Henning is in the forest whit his bike, Ron shoots him with a taser. Henning falls with his bike into the lake.
Henning is struggling between life and death. Philip decides to confess everything to Helen. If Henning's accident was orchestrated, it means there is a mole somewhere. Helen opens to Ron, and mentions the other witness. It is a mistake. Ron managed to find the identity of Philip and kidnapped him. But Philip had time to call Helen and tell him that he recognized the killer of the sandpit.