In this paper, we show that crises result from the combination of two parallel cumulative processes: first, an undercurrent accumulation of organizational imperfections that lay a favourable ground for crises to occur and second, the development of a growing ignorance that keeps managers blind to the presence of these imperfections. The central idea is to demonstrate that organizational imperfections are allowed to build up and grow into vulnerabilities because they are not noticed or taken into consideration. This managerial ignorance is described as a self-nourishing retreat from reality that decreases leaders' ability to pay sufficient attention to the increasing process of accumulation of imperfections and vulnerabilities. A case study in a French chain of supermarket is used to illustrate this process of crisis.