Stella Gibson is back on the trail of serial killer Paul Spector in TV’s darkest drama. We go behind the scenes in Belfast to find out what’s in store for season two

Deep within a former army barracks in Belfast, I am peering inside a car boot, looking for clues. Someone has set the vehicle on fire, but if they were hoping to destroy everything incriminating they’ve not done a great job. There’s a training shoe. A piece of a stocking. A trolley wheel. A bra. As in a real investigation, the vehicle has been sprayed with glue to make sure vital evidence doesn’t get blown away.

On the set of The Fall, attention to detail is all. Now returning for a second series, the drama concerns a meticulous psychopath (Paul Spector, played by Jamie Dornan) and the painstaking operation led by DI Stella Gibson (Gillian Anderson) that aims to catch him. Unlike most crime serials, The Fall isn’t a whodunnit but a whydunnit. It uses the time other shows might spend on red herrings to build intimate profiles of detective and criminal.

“That’s probably explored slightly more in the new series,” says 32-year-old Dornan, perspiring slightly after a game of football with the crew. “From Spector’s point of view, you might find out more about him and more about why he is the way he is, rather than the… doing.”

The Fall brings us up close to both parties, often uncomfortably so. We’ve seen Gibson wolfing down a room-service burger, and looked inside her post-coital bathroom bin. We’ve watched Spector stalking his victims but also washing his daughter’s hair and working as a bereavement counsellor. These chilling juxtapositions have proven addictive. Each episode of season one drew over 3 million viewers, and helped make Dornan a star, possibly at a price.

“In a worrying way, I find Paul relatable,” Dornan says. “There’s times when I scare myself how his reactions would be similar to mine. You carry some of that anger with you. You can’t fail to be left scarred by inhabiting something like that for two seasons.”

When I meet the cast of The Fall in May they are 13 weeks into a 16-week shoot. The show’s first series introduced us to Spector’s compartmentalised world of fetishes and compulsions, and his violent pathology. We observed how Gibson gradually pieces together his modus operandi: killing brunette women with good jobs; staging crime scenes; taking souvenirs.

The first series kept its main characters purposely apart. There were no showdowns, apart from in the last episode, when Gibson and Spector talked on the phone and Gibson revealed how far her investigation had progressed. We saw Spector and his family packing for a new life in Scotland. That unresolved ending was a “cop out” (nice pun, Daily Mail!), and “a big disappointment” (Radio Times). Twitter, uncharacteristically, was up in arms. On set, the producers explain it as the way of the TV world: they had to start small. Says Stephen Wright, commissioning editor for BBC Northern Ireland: “It was commissioned as a single series with an open-or-shut ending after the first five hours. We did the business and got a second series. That’s how it works.”

Written by Alan Cubitt (who also directs all six episodes), series two picks up the characters shortly after we left them, with things, in Wright’s words, “pitching to a climax”. Spector’s family return to the city, and Spector eventually does too, ostensibly to follow up on what Gibson told him in their conversation. But also, it appears, to return to killing.

There are complications. Gibson is attempting to take formal statements from key witness Rose Stagg. Meanwhile, Spector’s last victim has regained consciousness, and Gibson is determined to help salvage her repressed memories of the attack.

“It feels like a hunt,” says Gillian Anderson, now a producer on the show and evidently delighting in her claim to a cool character who gets results on her own terms. Sexually, Gibson is uncompromising. “There’s more about her… inclinations,” Anderson hints. “If not necessarily sex scenes.” As producer, does she now have a say who gets cast opposite her in such moments? She smirks: “I can’t say.”

Facebook Twitter Pinterest Serial thriller: Jamie Dornan as Paul Spector in The Fall. Photograph: Helen Sloan/BBC/The Fall 2 Limited/Helen Sloan

Gibson already has a strong recognition factor. Does she get reactions in the street? “I’m not in the street very much,” Anderson says drily. “But people are positive. When it was airing, it wasn’t so much ‘There’s Gillian Anderson’, it was ‘There’s Stella Gibson’. It was very different to other experiences I’ve had.”

Gibson is a character to fire the imagination. We don’t know much about her but Anderson sees this enigma as room to manoeuvre, a way to explore issues of gender equality and femininity. Gibson has got some secrets (“Aspects of her nature are very dark,” she says), and is persuasively tough. According to some media, she has even made white blouses iconic, which pleases Anderson. “I was trying to convince Stella McCartney to do a line of ‘Stella’ blouses,” she says, “but I don’t think she quite understood.”

The first character in a serial drama Anderson has played since the The X-Files, Gibson has had an effect on her. “There’s a level of self-respect, how she takes care of her clothes,” she says. “I started to pay more attention to that, and honour myself as a woman.”

Resourceful and clear-sighted, Gibson is the only person likely to catch Spector, and it’s the way the series captures his crimes that makes it uniquely unsettling. The camera builds a sense of homes and private spaces, and lingers forensically over the details in characters’ lives as a voyeur, criminal or detective might. When these spaces are later violated, it is hugely shocking. A sequence in the first episode of the new series is likely to make you levitate with anxiety.

“The more you draw the audience into a psychological relationship with the victims, the more impactful the dramatic moments will be,” says Alan Cubitt. “You don’t have to cut people up.”

The Fall has been criticised for its depiction of violence against women – an Express columnist called it a “glossy excuse for misogyny”. Cubitt feels those charges are unfair, or at least selective (although he has since admitted that the camera did linger too intimately on Spector’s acts). “Having seen The Returned, where a woman was walking in a PVC catsuit, then was stabbed in an eroticised manner by someone who tried to eat her internal organs,” he says, “I didn’t see how the Fall was overtly sensational.”

Cubitt was determined to make a drama that dissected male violence and sought veracity on screen. On set, the Guide visits two interrogation suites and an authentically chilly row of cells. In the evidence room next door, a specialist computer has been imported from Israel. Police officers have advised on everything from crime-scene procedure to car parking. Cubitt set Dornan serial-killer homework.

Facebook Twitter Pinterest The Fall Photograph: Helen Sloan

“Alan wrote me a list of rotten books, which I read in bed with my wife,” says Dornan. “Anyone can get an idea alarmingly quickly of what it’s like in the mind of some of these guys.”

Whereas Gillian Anderson has been a major name for 20 years, Dornan is in the odd situation of having become a heartthrob in the course of playing a psychopath. But he can see the funny side of being TV’s best-looking murderer (“Is it wrong to fancy a psychopath? Not really; each to their own,” he smiles). Even if the role has earned him the attention of Hollywood (if you didn’t know, he’s about to star in the adaptation of 50 Shades Of Grey) it has also got him “a few strange reactions” in the street. Given his character’s dual life, it’s not surprising.

“We see him in his family and professional worlds, and what he gets off on,” says Dornan, “the preparation for the kill, the act and the aftermath. Seeing them together like that is what I think is the genius of the show.”

Even though the story is set to move to a dramatic conclusion, it seems unlikely that a success like The Fall will be allowed to die with the Spector storyline. Might there be a series beyond it? “That sounds perfectly feasible to me,” says Dornan, who cautiously adds, “but I’m not sure I’d be involved…”

Gillian Anderson isn’t giving much away either, but as someone playing a cool, feminist cop on the way to becoming a classic character, equally she isn’t ruling anything out. So, is season two the end?

She smiles, very much as someone who knows something you don’t might: “Oh, I think there’ll be a third…”

The Fall starts on Thursday, 9pm, BBC2