In 1878 the Criminal Investigation Department replaced Scotland Yard's corrupt and discredited Detective Branch. In this classic story of the early days of detection, Joan Lock tells the fascinating story of the creation of the CID, the scandal which preceded it, and the successes and failures of the new organisation, including early cases such as the four murders by Ernest Southey, the ferocious outbreak of dockland killings in 1869 and the more familiar Bravo, Neill Cream and Jack the Ripper crimes. She describes Scotland Yard's gradual, if sometimes tardy, acceptance of identification and communication aids such as photography, the telegraph, telephone, Bertillon's anthropometric measurements and the fingerprint system. First World War spy and Dear John jealousy murders were followed by Roaring Twenties' swindles and the arrival of motor car bandits — which in turn led to the formation of the Flying Squad and the adoption of mobile wireless telegraphy. The introduction of women detectives is also discussed and the difficulties they experienced in establishing their place in a male dominated force. Joan Lock closes the gap between the academic police historian and the writer of popular true crime.