Robert Marsden was a real-life detective officer who served in the Liverpool City Police Force during the middle of the nineteenth century. His investigations took him from the dark and squalid courts of Liverpool's infamous Scotland Road and Vauxhall districts to the streets of New York City. Newspaper reports, police records, maps and contemporary photographs are used to tell his story. Detective Marsden gives us a unique and fascinating glimpse of Victorian Liverpool - the city known as 'Gateway to the Empire' and the 'black spot on the Mersey'.