The BRI acts in force in the flag of a collector victim of a burglary. Fire. Prosecution. The robbers abandon one of them murdered. The DPJ is on the case but Vallès old competitor Commissioner Pereggi, opposes their investigation. Falco and Romain have a choice: to investigate under the cloak ... Falco method that pushes through. Putting his superiors with a fait accompli, he infiltrates the gang of robbers, replacing at short notice slaughtered the victim. But the robbers, welded, believe incorrectly that their friend was killed by the BRI. One of them is lying, but which one? It will go through a museum robbery to find out.