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.

当一具被严重毁坏的尸体在巴黎北部铁路边一处垃圾场被发现后，巴黎警察部门总督察劳尔·伯托把握住了这次挽回名声的机会，带领小组成员追捕这名据信已经疯了的连环杀手。在逐渐揭开隐秘而残酷的卖淫集团神秘面纱的过程中，伯托内心的烦困让她的个人生活变得混乱，潜在的危险涌现了出来，她的个人世界已经处于崩溃边缘。　　与此同时，弗朗索瓦·罗班法官在调查涉及到重要政治人物的丑闻时过于耿直，树敌无数；职业生涯完美的皮埃尔·克莱门特检察官对正直的偏执令他的名声受到损害 ；雄心勃勃的律师约瑟芬·卡尔松因为一些危险的巧合让自己从一段不靠谱的合作关系中走了出来。当每个角色自己的齿轮转得失控，节奏加快了，人们交织在一起，私人生活和工作的界限逐渐模糊。

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.