A school excursion to Strasbourg Cathedral turns into a tragedy when a teacher is murdered in the cathedral square and nine children disappear. Young commissioner Maya Rosetti doubts her ability to handle a case involving children, so she ropes in her reluctant ex-partner, who's a psychologist used to working with children. The shocked parents pressure the police for answers, but the trail and motivation become increasingly complicated. 

Esther Lewanski is leaving the police, but on her last day becomes worried about Julia, a young mother who has disappeared, abandoning her baby Zoe. Despite the team's and Esther's efforts, Julia can't be found and, at the same time, a girl, Charlie, is found drowned. What's the connection between these two young women?