June 28th, 1914 : the murder of Austrian Archduke Franz Ferdinand is the beginning of the bloodiest conflict in History. The First World War mobilizes more than 60 million soldiers – civil and inexperienced people, for the majority of them - on the front lines. 10 million of them will lose their lives. The movie "14-18 - Hidden traces" is a scientific investigation. It is the discovery of unsuspected treasures that still lie under the ground of eastern France. Combining field research, laboratory analysis, historical anecdotes, interview of experts and 3D reconstructions, this documentary reveals a new and modern side of the life of the "Poilus" and the History of the First World War.