Critical infrastructures are receiving a great deal of attention, due, on the one hand, to the major malfunctions to which they are subject and their potential as targets of malicious intent on the other. Economic and political impacts are studied; increasingly high-performance technological solutions are put forth. And yet, these studies are very much marked by their systemic approach. In this article, the authors propose to look at a normally-insignificant event and highlight the different spheres (socio-political, economic, natural and technological) it consociates. Using an approach that combines human geography and the sociology of science and technology, this perspective allows us to have a more global view of the risks connected to critical infrastructures, which are characterized by their complexity and their high degree of interconnectedness.