While the Chernobyl and Fukushima accidents have raised the alarm about nuclear safety, the security of the installations, which are classified as defence secrets, is still shrouded in a thick mystery. However, in addition to the vulnerability of the sites highlighted by the operations of environmental activists, the investigation into the Brussels attacks in March 2016 revealed that Belgium's nuclear facilities were indeed a potential target for terrorists in search of weapons of mass destruction. From suicide bombings and the crashing of an airliner into a reactor to cyber attacks, drones, acts of sabotage and the homemade production of dirty bombs - a mixture of explosives and radioactive materials - the threats, recognised by experts, are real. So how are our facilities protected against these multiple risks, and how is the international community organised to secure materials and prevent trafficking?

From the United States to Germany, France and Belgium, this investigation reveals the abysmal flaws in the protection systems of nuclear sites, most of which were designed before the attacks of 11 September 2001. Interviewing experts, politicians and Greenpeace activists, the film also shows how the nuclear industry, now often loss-making and over-indebted, is struggling to implement effective - and inevitably costly - measures to deal with the risk of terrorism. We discover that no international standards are imposed on nuclear states, particularly when it comes to securing the most dangerous materials, despite the attempts of Barack Obama, initiator of the World Summit on Nuclear Security... The silence that surrounds this threat in the name of confidentiality in the face of a potential enemy also deprives civil society of the legitimate debate on its security, when the decisions to guarantee it are a political matter. A chilling investigation into one of the world's best-kept secrets.