'I was pretty broken when filming ended - I had to take 2 months off'
As the gripping adaptation Dublin Murders hits our screens, Gemma Dunn speaks with creator Sarah Phelps and stars Killian Scott and Sarah Greene about the masterful reworking of Tana French’s novels
Sarah Phelps is showing off her latest tattoo - in her own words "a rather clumsy hawthorn leaf".
The screenwriter - best known for her work on EastEnders and various serial adaptations - admits it was in fact inspired by an episode of Countryfile.
"They were in Northern Ireland and they interviewed this guy who had a Marxist-Leninist cap, an amazing swoosh of grey hair and an anorak with loads of pin badges," she says.
"He was protesting about a motorway that was going to destroy a hawthorn tree, which was the 'magic fairy tree of Ireland - if you cut it down, everything will be disrupted, you cannot upset the fates'.
"He won because at some deep, metaphysical level every person involved [must have] woken up at 4am and thought, 'What if he's right? What if you cut down that tree and all hell breaks loose?'
"That was the thing that made me sit bolt upright."
Phelps is talking at the screening of her latest, and rather fitting project, Dublin Murders.
The RTE and BBC crime thriller - drawn from Tana French's compelling Dublin Murder Squad novels - is billed to deliver a dark psychological mystery with a taproot that drops deep down into Ireland's past, foreshadows the future and brings insight to its present.
Set at the height of the Celtic Tiger, the eight-part series will focus on two murder investigations led by ambitious detectives Rob Reilly and Cassie Maddox, played by Killian Scott and Sarah Greene.
It was a huge undertaking for creator and writer Phelps, who opted to blend French's first two novels, In The Woods and The Likeness, into one text.
"I plaited them because the first one is all about Rob and Cassie as the baseline and then it's all about Cassie and another detective - and I thought, 'I don't want to do that'," says Phelps, whose incredible reworkings include everything from Agatha Christie to Charles Dickens and JK Rowling.
"This is about friendship, shared secrets and shared lives. It's about compromise and heartbreak and the dark places we go to and the things that scratch at the back of our skulls.
"I put them together, so the consequences are overwhelming for both of them at the same time," she says, quick to add: "When you say that out loud it sounds easy, but I was like, 'F**king hell, I've actually got to do it!'."
What can its lead stars tell us?
"It follows Rob and Cassie in Dublin as they investigate a murder in 2006," says Scott (34), who had to shield his own Irish roots to perfect an English accent for his part.
"Then, due to the location of the body, there's a suspicion, between themselves, that it might be connected to a historic case 20 years ago when three children went into the woods."
Penny Dreadful star Greene (35) adds: "The whole show is about their secrets.
"They're thick as thieves and they're really good partners who finish each other's sentences. But I think they have a shared guilt of surviving.
"They both survived traumas in their pasts and that binds them together.
"They're each other's keeper of secrets and it might not be the healthiest of relationships between the two of them."
Scott, who has previously starred in Strike and Love/Hate, says: "There's an outsider quality to both of them.
"Rob is someone who's really disturbed but has been managing to keep a facade on it to this position alongside Cassie as a hotshot detective.
"It's a performance that's been very effective thus far, but it seems to be coming to a point now where that mask is beginning to crumble.
"It's about keeping things together but there's a breaking point."
With high emotion, high action and a seven-month shoot that spanned Belfast and Dublin, it wasn't just the characters that needed a breather.
"We were very lucky in terms of the company of people we had. Sarah is wonderful and it was a very easy process," Scott says.
"But you do get to a stage where you're exhausted.
"Although that's not the worst place for an actor to be because they're turning off their critical brain and just doing it."
Greene adds: "I agree completely with Killian.
"I felt completely satisfied by the work, but I was pretty broken by the end of it. I took two months off."
Phelps says: "Productions have their own energy, they become their own beast.
"Over eight episodes and seven months, you've taken people who look like normal human beings and broken them into a thousand tiny pieces.
"The theory on this one [was] no one is allowed to go to bed.
"We are in this totally immersive world and we end these characters' stories at the end. We can't end one story in the middle and start another story, they've got to be plaited. There's no room to breathe.
"This world of the wood is immersive, and it holds these two characters in this bell jar which is not going to let them escape unless one of them punches through it."
So what's the overriding message?
"The world of Dublin Murders is part psychological thriller, part police investigation, with a shiver of modern Gothic," says Phelps, who has already shown interest in a second run of the series.
"It's about the borderlands between memory and forgetting, madness and sanity, between the present and the voracious pull of the past.
"With taproots sunk deep into the oldest folk tales of children who go under the hill, fetches and feys.
"It's a story about the terrible things we do when we think no one can see us, when we think we can get away with it," she adds.
"It's a love story about the search for forgiveness, for some tiny shining tenderness to guide us home."
Dublin Murders starts on October 14 on BBC One and October 16 on RTE One