Keeley Hawes: I found The Missing too traumatic to watch

But when she came to be cast in the second series of The Missing, which flips the plot to tell the story of an abducted child who comes back to her family, Hawes was forced to imagine any mother’s worst nightmare.

“We all know the story about Madeleine McCann,” she says. “There’s this line that Kate McCann wrote in her book that really stuck with me. I kept thinking about it. She wrote, ‘Every morning you wake up and think, is today the day?’ Well, in our story, today is the day."

Hawes plays Gemma, the wife of Sam (David Morrissey), and in a twist typical of the work of Harry and Jack Williams, who wrote the first series, they are a couple who have managed not to let the abduction of their daughter destroy their lives.

“The family have moved on,”
says Hawes, “because they have to get on with their lives — how people get on in this situation I have no idea, but they do. Then they get the call to say that their daughter might have been found. This girl has come back. But then it turns into a story of ‘be careful what you wish for.’”

Hawes is reluctant to say any more about the storyline, which is split between 2014 and 2016, just as the first series straddled two timeframes.

It also contains the Williams brothers’ trademark mix of plot switchbacks and surprises.

“Almost everything I can tell you is a spoiler!” says Hawes. “But people love to second-guess. When I did Line of Duty people were sending photographs of white boards they’d set up trying to figure it out. This will be the same.”

What she will say is that for her character things start out badly — there’s something about the returned daughter that doesn’t convince her mother.

“And then every time you think it can’t get any worse it does. There’s nothing this family don’t go through.”

Did she mine her own experiences as a mother in order to reach those emotional depths? “It would be one way but it’s not a healthy way, it’s really not. I learnt a long time ago that you can’t work like that. And anyway, why would you do that to yourself? Why would I put those images in my mind? It’s acting. I don’t need to summon up some terrible image of my own child.”

Instead, she had terrible images on her doorstep. The Missing was shot on location in Germany and Belgium, and Hawes was in Brussels when the coordinated suicide bombings took place across the city in March.

“We were shooting on the day it happened. We were all on our way into work and everybody was arriving when the news broke. The atmosphere was one I hope never to have to go through again. But by the time we went home that night the city was back up and running and all of the buildings had flags flying, so we saw both sides.”

The Missing begins tonight on BBC1 at 9pm

Meet the cast of The Missing series 2