It is, it has to be said, one of the bleaker sets for a TV show that I have ever visited. I am trying in vain to shelter from the pouring rain at a cheerless cemetery in the industrial outskirts of Brussels. Welcome to the second series of The Missing.

The setting is quite appropriate for this riveting British drama, however.

The co-star of this season, Keeley Hawes, sighs that, “Today we’re filming funerals and cemeteries, so my head is full of that. But it’s right that The Missing is serious. It’s absolutely superb drama.”

She is correct, of course. As its title suggests, The Missing is known for its deeply disturbing themes. This drama, which enjoyed a hugely popular first run last year, netting more than seven million viewers an episode in the UK alone, quite rightly takes its grave subject matter seriously indeed.

In a bold move, the second season of Harry and Jack Williams’ acclaimed drama starts with an almost entirely clean slate. It dispenses with most of the characters from the first series, except the dogged French copper, Julien Baptiste (played by Tcheky Karyo).

This year the story focuses on Sam Webster (David Morrissey, The Walking Dead), a British Army captain stationed in Germany, and his wife Gemma (Hawes), whose daughter Alice disappeared in 2003.

Eleven years on, a young British woman (Abigail Hardingham) turns up, seemingly out of nowhere, teetering along the streets of a German town before buckling and falling to the ground. She claims to be Alice Webster.

As the plot shifts between 2003, 2014 and the present day, we witness the cataclysmic effect that Alice’s reappearance has on her family.

Her parents’ lives are turned upside down. Meanwhile, Julien Baptiste, the French missing person’s detective from the first series, rushes across Europe to take on this cold case.

The story centres on the complex feelings that are uncorked when the missing child a family have been pining for suddenly turns up again. As you can imagine, this highly unsettling drama puts its characters – and its audience – through the emotional wringer.

But for all that, like the first series, the second run of The Missing is absolutely riveting.

Hawes, who is happily married to actor Matthew Macfadyen and has three children, agrees.

“Once I started reading the script, I couldn’t put it down. It’s like picking up a brilliant novel. You just can’t stop reading it.”

Forty-year-old Hawes, who has starred in Line Of Duty, Spooks, Ashes To Ashes and The Durrells, says her character is still perturbed even when Alice shows up again.

“Gemma doesn’t have maternal instincts and she wants to so badly. That’s all she’s thought about for 11 years.”

Playing tormented characters is clearly far from easy. But actors sometimes have to visit dark places when they are appearing in a potent drama such as The Missing.

Morrissey, who is married to the author Esther Freud and has three children, reflects that, “As an actor, you have to draw on lots of things.”

The 52-year-old actor, who has also starred in Doctor Who, State Of Play, The Deal, Blackpool, The Driver, Red Riding and Sense And Sensibility, adds that it helps that, “I’m a bit of a worrier in real life anyway. This drama is all about those things. I even worry if one of my children is trying to get a jar off the top shelf.”

Hawes chips in that, “I found researching it very intriguing. But all the places you have to go with that and all the battles Gemma and Sam have to stay together – that’s unimaginable, really.”

Despite some scenes being tough, Keeley says she has been able to leave her troubled character behind at the end of each day.

“My life is so busy with my three kids and my days are so full that I have no time to dwell on things. That’s a good thing.”

So have either of the stars of The Missing momentarily lost a child?

“No,” replies Morrissey. “I’ve never lost a child in a supermarket or anything like that.

“There is always that fear inside one about that, but I’ve never had that as a parent. Maybe because I’m always with my children saying, ‘Be careful’.”

He jokes: “My son is 21 years old now and I’ve still got him on reins.”

The Missing, TVNZ 1, starts Tuesday March 28.