City of Darkness takes place in 1888 London, where Jack the Ripper roams the streets with impunity and Scotland Yard seems helpless to stop him. The science of forensics is in its infancy but a few detectives - Trevor Welles among them - recognize that they are dealing with a different sort of killer, a "modern criminal" who chooses his victims at random. If Jack is to be caught, he won't be caught with Scotland Yard's normal methods of deduction...