This paper explores police misunderstandings of the organization of theft interwar England. It is based on a whole network analysis of a Newcastle Police identification book of all thieves and suspected thieves known to local detectives. The book is the only surviving example of a once common policing tool. It records individual and relational data about 116 men born between 1878 and 1915, who police considered active criminals in the period 1922-1936. A comparison of the main network components with a fuller accounting for their members' ties using census data, newspaper reports and habitual criminal registers reveals gaps in police intelligence. The findings suggest that interwar police considered professional theft a craft crime involving men working alone or in small teams. This police focus on front-line operators left them with a misleading image of a large fragmented network of working-class criminals. This image informed police rules of thumb that guided street-level decisions, and influenced sociological understanding of criminal organization before the 1960s.