As the new magistrates of Westminster, novelist Henry Fielding and his blind half-brother John want to set up a police force to tackle London's soaring crime epidemic. They find a potential patron in Lord Newcastle, the Prime Minister's brother, but he is unsure of such a force's merits. With the help of Saunders Welch, the High Constable of Holborn, the brothers set out to show Newcastle they can rid the streets of the violent criminal gangs.