On Christmas Eve, 1888, a mysterious stranger arrives in the small Herefordshire market town of Ledbury, intent on a curious mission. A few days later, as the Ledbury Lamplighters celebrate the end of the year by extinguishing the town's lamps, a prominent local businessman is murdered in full view of partygoers. Detective Inspector Samuel Ravenscroft is once again reunited with his old friend and colleague, Constable Tom Crabb. As they embark upon their most dangerous adventure yet, they gradually unravel a sequence of events that threatens the very political and social stability of the country. Meanwhile, the man known as the Whitechapel murderer returns from exile to carry out one final assignment for his new masters.