Season 4 opens with Eliza having taken over the business of Nash & Sons (not that he has any sons) and things are not going entirely smoothly, although help comes from some familiar sources. Outside of work, her relationship with William (The Duke) builds towards a looming decision that will shape both their lives.

In fact, Eliza teams up with Duke to investigate a burglary in a high-end brothel whose clients include important members of the British government.