(upbeat music) - What do you mean she's a private detective?

What nonsense?

(glass breaking) - We left off in season 3 with Eliza undecided as to whether she would join Nash's agency and season 4 begins with her decision made.

Here at Nash and Sons, we offer the most professional of services.

And I do not boast when I say that these past few months under my leadership have seen even greater success.

- You're under arrest.

- [Rachael] We hit the ground running and we opened with Eliza in this hugely busy office.

- Another successful conclusion to one of our many cases.

- Our first instinct is, wow, she's this huge success story, but all is not what it seems.

- The once most successful private investigation agency in London is now on the verge of collapse and it's all thanks to the lady detective.

- I leave you a business that is thriving and come back to find it barely surviving.

- Stubbornness is one of her greatest qualities, but that doesn't help her when she's working in an office full of people because at the end of the day she's a maverick, not a manager.

- [Man] Sir.

- Not now.

- [Rachael] In season 4 Duke is really under pressure.

Over the season we see the pressure building in him-- - We're going in.

- To the point where he puts himself in a situation that could have gone very badly wrong.

(door banging) - Police!

- There's a lot of revelations.

- You look tired.

- You look beautiful.

- We get to see Eliza and Duke really move forward in their relationship.

- Something has to change, Eliza, perhaps for you, perhaps for me.

You are good detective, Eliza, and whatever happens from here, you'll find a way to make it work.

- Where they go from here, I don't know myself.

I'll be really excited to find out.

(soft string music)

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