In a gut-wrenching scene via correspondence, Eliza writes to the Duke in New York, confessing her struggles. He writes back—solicitous but distant—proving that the Atlantic Ocean is wider than just geography. The episode masterfully uses silence; the absence of the Duke’s booming voice in her office is a character in itself.
So, is the Duke gone for good? Not entirely. Martin appears in a limited capacity, acting as a narrative bridge. The season premiere cleverly writes Wellington out by having him accept a prestigious position at the New York Police Department. This transatlantic move leaves Eliza (Kate Phillips) utterly alone in London.
Have you watched Season 4? Do you prefer Eliza with the Duke or Alexander Blake? Let us know in the comments below.
That threat is The Crimson Alliance , a shadowy syndicate of corrupt industrialists and police officers. Fitzroy is a member. Blake used to work for them. And Eliza, unknowingly, is hired to investigate a crime that leads directly to their door.
This moment defines Season 4. Eliza Scarlet is no longer a girl waiting to be chosen. She is a woman deciding who is worthy of her partnership. By the finale, she kisses Blake—not with passion, but with calculation. It is a kiss of acceptance, not surrender. The final episode brings the Duke back for one crucial scene. William Wellington returns to London to collect his remaining belongings. Seeing Eliza running the agency with Blake by her side, the Duke has a moment of quiet devastation. Stuart Martin plays this with heartbreaking subtlety—a single tear, a forced smile, and a goodbye that feels permanent.
Trapped in a stalled carriage during a storm, Blake confesses that he isn't helping her for justice, but because he is "infatuated with her stubbornness." It’s a raw, whiskey-soaked confession that feels earned. However, unlike her moments with the Duke, Eliza does not blush. She analyzes. She asks, "Are you confessing love or leverage?"
To survive, Eliza takes a case involving a missing aristocrat’s daughter. This case forces her to team up with the one man she swore she never would: Alexander Blake (Tom Durant-Pritchard), a charismatic, roguish ex-convict turned informant. If the Duke is order, Alexander Blake is chaos. Introduced as a morally grey fixer with a silk scarf and a silver tongue, Blake is the most dangerous addition to Season 4. He isn't interested in rules; he is interested in results.
For those willing to let go of the past, Season 4 offers the sharpest writing, the highest stakes, and the most authentic portrayal of a single, working woman in the 19th century since Victoria . Stream it on PBS Masterpiece or Amazon Prime Video. Just bring tissues—not for the mystery, but for the goodbye.