Here's how Ardal O'Hanlon's DI Jack Mooney left Death in Paradise

So by the end of episode four, Jack was on his way and the Shack once again stood empty. Here's how it all unfolded:

Why did DI Jack Mooney leave? What was his exit storyline?

At first, it looked like Jack might be follow in the footsteps of his predecessor DI Humphrey Goodman (Kris Marshall) and leave Saint Marie for the sake of *love*. As Death in Paradise fans will recall, Humphrey quit his Caribbean police job in series six so he could make a new life in London with Martha – after their holiday fling turned into something much more serious.

Anna and Jack seemed also to be getting serious, with Anna inviting Jack to join her on her travels – and Jack introducing Anna to his daughter, Siobhan (Grace Stone).

"I thought maybe you could join me in San Francisco at the end of the month, and then we could drive through the midwest together before heading South for the carnivals," Anna suggested. And while Jack was talking as if he were really going, Anna did comment: "We've been talking for ages but your father here still has not told me if he will be coming with me yet..."

However, Jack also had something else to think about.

Daughter Siobhan, who'd spent the last few years at university in the UK, had just arrived in Saint Marie for a week's holiday.

"Well I've just finished uni, and as of yesterday I've got a job to go back to," she informed him and Anna over a drink at Katherine's Bar. "It's a publishing company back in London, so after three years away it'll be nice living back there. See all my old friends, family. I'm going to be coming back home."

That seems to have planted an idea in her dad's mind. "Hard to believe, my little baby going out into the world. All grown up," he said, looking pensive.

Grace Stone plays Siobhan Mooney in Death in Paradise

Next came a thought-provoking chat with the Commissioner over a glass of rum.

"As a young man, I thought about travelling the world," he said. But he didn't – and has no regrets. "Why would I? I've had a wonderful life here. I'd regret missing even a day of the life I've had."

"You see, that's what I'm missing," Jack said. "The thing that left me the day that Kathleen passed away. That sense of knowing where you want to be, and being there."

The wise Commissioner spilled some more words of wisdom: "Some might say that travelling's a way of finding that. I think I say that true happiness has very little to do with geography."

So what was Jack going to do?

The answer came when he turned up on Anna's porch and declined both a glass of rum and a seat next to her on the plane. "I won't, actually," he said. "Anna, I won't be coming with you on the trip."

"Of course you won't," she replied. "I never really thought you would, Jack. I don't blame you, you lost your wife, your life came crashing down around your ears, and so you ran away. There's no shame in that."

And while Jack sees going travelling as also "running away", for Anna it's a different thing entirely: "Actually I'm doing the exact opposite. You see, I was in an unhappy marriage, so all the time I was running away from who I truly am. So travelling the world is me, finally being myself. Being honest."

"But that's what I'm doing too," Jack insisted, before dropping the second part of his big news: "By going home.

"You see, I finally worked it out. Losing Kathleen, well – that was only part of the whole grieving process. When she died, I lost the rest of my life too. My life is back there in London, my house is sitting there empty. That's my home. My friends still go to the local for a beer and a big moan, and now Siobhan is going back, back to our home. So gallivanting around the world with you, as amazing as that would be – and I know it would be amazing, I know that – but that would be me just running away again. And I've done enough running. I'm going home."

As for the future of Anna and Jack's relationship? It might still happen, once Jack is back in London and Anna returns from her travels. "I will make London my last stop," she said, while Jack promised: "And I'll put the kettle on."