Laure and her team are on the trail of Sophie Mazerat, a student whose car has been traced to the dumping of the bomb-damaged body, and arrest her at the university. Karlsson's attempts to have Moussa Kone freed from detention are hindered when Thomas's cell arranges a vicious reprisal attack against the bank which reported him. New boss Herville is making his presence felt in the squad room and nobody is liking his business methods, especially when this leads directly to the squad losing touch with their best lead in this most complicated of cases.