When teenager Lea does not return home from a music festival, her parents contact the police, who uncover areas of Lea's life that her family knows nothing about.

Lea's father Julien is in police custody for lying about his alibi and refusing to give his actual whereabouts on the night of his daughter's disappearance. Molina and Camille discover that Lea has been introduced to single-seater racing, but wonder how she managed to pay for lessons.

Julien is woken by a frantic message on his mobile phone from Lea asking him to call her. Molina and his team trace the call to the train station. Nicolas, a waiter at Morel and Sons restaurant, shows Julien the illegal police radio interceptor he has in his car, and as Julien listens to the communications, he begins to shadow their investigations.

Francis Dupuis is interrogated about the murder of Lea Morel, but he is obviously confused and unclear about details despite his confession. However, when the police search his property they make a surprising and convincing discovery.

The waiting is finally over for the distraught Morel family when Lea's body is found in Miribel lake. As they prepare for the funeral, Julien becomes obsessed with identifying everybody who attended her birthday party on the day she went missing, and manages to identify someone who looks out of place in the club.

An apparent suicide with a long confession seemingly concludes the case of Lea's murder, but Molina is not convinced.

A jeweller identifies the man who bought the pendant found in a grave dug for Lea Morel. The man is questioned, but he has an alibi for the night of the murder. Romain is given a bag of Lea's possessions left at the race track and finds a USB stick with incriminating evidence.

Molina decides that the police have been chasing a red herring and retraces their investigation into Nicolas Barrault. A search of his possessions turns up one of Jenny's business cards with a handwritten note on the back.