This article asks why and how governments keep secrets from publics, journalists and politicians using the strategy of ‘cover storying’. To develop a theory of cover storying, insights are drawn from political sociologies of state secrecy and from recent sociological examinations of secrecy and deception in organisations. This theory is illustrated by analysing Cobra Mist, a secretive and deceptive Anglo-American Cold War intelligence operation. Examining recently declassified documents, this article develops a framework for the analysis of five interrelated narrative conditions that shape social processes of cover storying: correspondence; plausibility; accountability; constraint; and durability. In conclusion this article reflects on the broader implications of this analysis for contemporary state and organisational theories and understandings of secrecy.