Hands Up! in the World of Crime: Or 12 Years a Detective is a firsthand account of Clifton R. Woolridge's twelve-year career on the Chicago Police force at the turn of the twentieth century. The narrative recounts the author?s experiences in investigating and combating crime, drawing on personal memoranda, newspaper reports, and official police records. It includes vivid descriptions of arrests, the pursuit of bank robbers, confidence men, safe blowers, diamond thieves, and other criminals, as well as commentary on legal procedure, law enforcement challenges, and interactions with media and civic authorities. Hands Up! in the World of Crime presents a detailed autobiographical and professional narrative by Clifton R. Woolridge, a veteran detective of the Chicago Police Department. The work situates Woolridge's career within the evolving practices of early modern policing and urban crime control in the United States. Utilizing personal memoranda, newspaper accounts, and official records, the text recounts thousands of arrests, high-profile criminal cases, and routine investigative operations. Case stories span bank robberies, confidence schemes, violent offenses, safe-blowing incidents, and the rescue of victims from vice networks, illustrating both procedural tactics and the socio-legal context of late nineteenth- and early twentieth-century law enforcement. The narrative underscores the interface between detective work, public administration, and media representation, offering rich primary source material for historical criminology, police studies, and the cultural history of crime in urban America. Clifton R. Woolridge was a Chicago police detective whose experiences in active service formed the basis of this memoir-style account. Although detailed biographical records are limited, the book positions him as an embedded observer of criminal justice practice, documenting his law enforcement career during a period of institutional consolidation for urban police forces. His narrative reflects firsthand insight into procedural norms, investigative challenges, and institutional dynamics within the Chicago Police Department at the early twentieth century.