London 1830. John Marlott escapes the Bethlem Hospital seeking his revenge on Lord Daniel Hervey. The hunter soon becomes the hunted.

John Marlott adopts a new identity and gains employment. He believes someone is lying about the recent murders of local clergymen and he is determined to uncover the truth in his search for justice.

Marlott is convinced that Billy Oates and the origin of the fever killing local families will lead him to Lord Daniel Hervey.

An unexpected encounter with the mysterious Frederick Dipple suggests that Marlott needs to protect his allies, who he realizes are increasingly in danger.

Marlott's new intelligence brings him closer to a solution and leads him to an apparently deserted tower. However, there are darker and colder dangers inside.

As the police close in John Marlott needs to rescue Esther from Hervey and Dipple, and resurrect both his own and her fortunes in an epic season finale.