Police commissioner Herville is found dead in a Chinese restaurant in the 13th arrondissement of Paris. Gilou must break the news to Laure, who is being treated in a Police rehabilitation center. Now in charge of the unit, Gilou begins investigating with Ali, a young cop, fresh out of training. They quickly find themselves on the case of a break-in gone wrong and the trail of 15-year-old Ryan, a juvenile delinquent. Roban learns he must soon retire but still manages to oversee the Herville case. Awaiting trail, Joséphine struggles with life in prison.

Police captain Laure Bertraud returns to work as she and her team begin a complex new investigation after a human torso is discovered in a pile of garbage in the 20th arrondissement in Paris. Meanwhile, a high profile criminal trial tempts ambitious lawyer Joséphine Karlsson, and Judge Roban faces a health crisis. This new season pushes every character to their limit, and forces them all to question long-standing affiliations and beliefs.