A break-in at a sugar merchant's Mayfair home brings the Bow Street Runners into conflict with their patron, Lord Newcastle. He reminds the Fielding brothers that their prime duty is to protect the property of the rich and yet the number of burglaries has increased under their new police force. Determined to prove him wrong, the brothers search for the Irish suspects in the shanty towns of Covent Garden, known as the Seven Dials.

The Fielding brothers are dining at a tavern run by Jack Harris, an infamous pimp, when a messenger announces that a woman's body has been found at a nearby bagnio. Despite being raped and horrifically mutilated, the woman, Ann Bell, miraculously survives. Tensions mount as the murderer's identity continues to elude the Runners and they fear embarrassment by failing in their first case…

When the Reverend Erasmus Cavendish is found murdered in his Soho church, his maid informs the Runners that the reverend was a homosexual (a crime punishable by hanging) and points the finger at a man named William Flynn as the prime suspect. The Runners take their search to Miss Suki's 'Molly House,' an infamous brothel and rendezvous for London's gay men.

Tom Jones, an infamous gang leader, is broken out of jail by his Irish gang, who maim several prison guards along the way. This high-profile jailbreak questions the authority of the Bow Street Runners and risks making Lord Newcastle look very foolish for supporting them. The Runners travel to the Seven Dials to re-arrest Jones. With Lord Newcastle reviewing the Runners' government allowance, Henry Fielding accompanies them to make sure Jones is apprehended.

Henry looks back on the struggle to fund the Bow Street Runners in the first place, and reflects on how close London came to not having a police force at all… 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.