- Arabella is a pretty steadfast, determined, joyful lady who had a relationship with Eliza when they were kids.

Then they reenter each other's lives.

- Oh, no.

It is her.

- Who?

- Arabella Herbert.

We were at school together, she was the most dreadful girl.

Don't look.

- I think you can see throughout the show a lot of, a lot of different layers of Arabella.

So yeah, it's been exciting.

- Well, we mustn't keep you from your dining companions.

- Oh, no, I'm not a customer.

This is my restaurant.

I own it.

It is called Arabella's, after all.

- Perhaps if they didn't have such a painful relationship, or a painful past, then they might actually spark up a really solid friendship.

But I think that ship's sailed.

- Do you remember that Victoria sponge cake?

You almost burnt the school down.

Ms. Dawkins was not amused.

- Well, we were young children, so.

- Not that young.

Shall we?

- You know, Arabella people might remember was, you know, spoke off in season one as being this girl in Eliza's class who wasn't particularly nice to Eliza.

- You don't remember how you behaved towards me day after day, year after year?

- We were children, Eliza.

What is the connection between our school days and this investigation?

- Your character.

- Brings a lot of sort of questions up and a lot of emotions up.

- It's genuine attraction with him when she first sees him.

And I think it's reciprocated - Anyway, good day Mrs. Acaster.

- Arabella, please.

- He allows her to be witty and playful, and obviously he's a very attractive man.

So, I mean, who wouldn't?

- Arabella in a way, she's all those bits that Eliza can't be, or won't be cause of her job and because of her career.

- These are wonderful.

- The pleasure is all mine.

I miss having a man to feed.

- The Duke sees that and she's just sort of slid into that place that Eliza can't be for him.

(gentle music) - I think the look on Eliza's face at the end of episode four says it all.

(gentle music) It just changes the whole, her whole world.

So she's gotta kind of work out how they can coexist together with this new person in his life.

And can they?

- So yeah, it's a difficult relationship, and it definitely puts a lot of sort of drama and emotions into it, for both Eliza and Duke.

(gentle music)