“This is one of those big national stories that affected people at the time, and has never been solved,” Nicola Walker tells us on a break between scenes at ‘police HQ’, where her Unforgotten character DCI Cassie Stewart is hard at work on her latest cold case.
And this cold case will take us into new territory, because series three’s victim is a teenage girl whose disappearance at the turn of the Millennium sparked huge public interest. Her body was never found – until now.
“It’s one of those stories that people will have written books about, there will have been plays about it, there will have been TV programmes about it,” Walker explains. “It’s one of those big iconic murders that wasn’t solved.”
“You think, oh these are the ones we all feel a collective response to, and a collective grief about when they happen,” Walker says. “In our lifetime we’ve all got ones that we can say, that you think, ‘I remember that. I remember where I was when I heard about that.'”
The ITV drama begins with the discovery of human remains at a building site just off the M1 motorway, and the introduction of a new cast of suspects: four old friends, played by Alex Jennings, Neil Morrissey, James Fleet and Kevin McNally.
But by making this cold case an “iconic” disappearance, writer Chris Lang has brought a new dimension to series three. What happens when the police come under public scrutiny? What role will social media play? How will Cassie handle the spotlight of media attention?
“When the first series came out I thought, and I think we all did, it came out and it got wonderfully received and you think, oh no, it’s the difficult second album time,” Walker admits.
“And he came back with that second series that – he just shifts things. he’s not interested in repeating himself, it seems to me.
“There’s some really interesting stuff where Cassie has to deal with the media for the first time and there’s an extra layer of difficulty in her job, being the public face of a case that, 18 years on, there are questions about whether or not something went very very wrong back then. And she’s the public face of that.”
Question marks over the original police investigation mean Cassie and Sunny must take a closer look not just at the suspects and the victims, but also at their own institution. The implications of this crime reach out further and further.
“You find this body and you try to go back, find out where it went wrong, and try to make it right,” Walker says.
“And the effect it had on the community – because you’ve now got a community that was known for this crime and is always now, ever since been known for this crime. It’s that stain that never goes away that’s affected a wider community than the family.”
Unforgotten will return for series three on Sunday 15th July at 9pm on ITV
Sign up to the Radio Times newsletter for the latest TV and entertainment news