Louise Morvan is finally going to shed light on the mysterious death of her uncle, Julian Eden, whose agency she inherited. Commissioner Clémenti offers her a primary lead. He found the cop from whom the dossier was taken away and who was transferred to the provinces in 1979. The young woman’s solitary quest begins in Strasbourg. Meanwhile in Paris, Clémenti must flush out the “riverside killer”, a bloody assassin of the homeless.