Despite the strong objections of Beckriche, Laure, Gilou and Fromentin are convinced that they must stay on the trail of the Camara brothers. They discover that their homework is only a facade, behind which lies a traffic of contraband cigarettes. In the field, Gilou confesses the whole truth to Laure about the bullion. For his part, Tintin has to deal with the arrival of his son Ruben, who came to spend a few days with his father. In addition, Laure's investigation into Josephine's rape is progressing.

Le commissaire Beckriche est furieux de voir l'enquête piétiner. Gilou avoue à Laure avoir volé deux lingots d'or appartenant aux frères Camara. Celle-ci lui demande de garder le secret sur cette faute. Les deux policiers découvrent que l'association d'aide aux devoirs mise en place par les Camara sert de cache à un trafic de cigarettes de contrebande. De son côté, Joséphine est persuadée qu'elle a été agressée par Eric Edelman, mais reste incapable de le prouver.