H Division and the Independent City of London force are thrown together when the panic surrounding a sudden cholera outbreak leads them to scour both boroughs to find some underlying pattern amidst the rising tide of sickness and death. Meanwhile Emily Reid seeks patronage for her charity efforts, unaware of the resistance she will meet.

A string of brilliantly masterminded robberies draw the attention of Reid and his team. While Jackson works to trace the thieves' hardware, Drake is confronted with a spectre from his past in the form of his onetime Colonel. As Reid closes in on the brash robbers and their ultimate target, Drake finds his loyalties put to the ultimate test.