As an icy wind blows through the city, a primary school teacher is murdered in front of Strasbourg cathedral, and her nine pupils go missing without trace. Young superintendent Maya Rosetti is put in charge of the investigation.

When Julia, a suspect in the disappearance of her daughter Zoé, goes missing, former policewoman Esther Lewanski returns to the force and joins the investigation to prove her friend's innocence.

Despite his apparently placid life, Tony makes ends meet by selling drugs, until the death by overdose of one of his customers. Superintendent Maya Rossetti wonders if there is a link between the death and the kidnapping of Prosecutor Dassault.

Lisa Ferrer, an ambitious young exec at a pharmaceutical company, has gone missing after experiencing complicated workplace conflict and mental health problems. Newly appointed judge Leo Etchegarray joins the police team for the search.

Commander Gabrielle Perez hunts for 11-year-old boy Elouan when he vanishes from hospital. Gabrielle and her assistant Alaoui learn that the family history is complicated, and they must investigate quickly, as Elouan's life is at risk.