The most repulsive drama ever broadcast on British TV is back. Not everyone agreed with that Daily Mail description of The Fall; indeed, it was BBC2’s most popular drama for 20 years and its return is one of the most eagerly awaited TV events of 2014.

When it aired in 2013, The Fall – starring Jamie Dornan as the hunted and Gillian Anderson as the hunter – made for particularly difficult viewing. At a preview screening on Tuesday night in London, the first episode of the second series revealed itself to be gripping but a slow-burner unlikely to win over new fans. I spent the first 30 minutes wanting to see more from Dornan, as estranged family man/serial-killer Paul Spector, and the second half with my hands over my face. That’s entertainment? Probably.

Set 10 days after the final episode of series one (open-ended cop-out? I rather liked it), the second season opens with both Dornan and Gillian Anderson’s DSI Stella Gibson in glorious isolation. Dornan literally so; though Gibson, seconded from the Met Police to root out bent Belfast coppers, has always been an island.

“I look the same but I am not the same as before,” says one of the victims. Neither is the drama. Spector’s pretence of being an ordinary family man, the double life that gripped in its first run, is all but shattered. But not entirely so. At a Q&A following the screening, writer Allan Cubitt, who also directs this six-part series, described Spector’s daughter, Olivia, as “the heart of the thing. She is the most distressing victim in The Fall.”

Dornan said the script “transcended everything I thought it could be. You will see as the series goes on it is quite remarkable what it entails.”

Jamie Dornan plays serial killer Paul Spector alongside Gillian Anderson’s DSI Stella Gibson in The Fall. Photograph: Steffan Hill/BBC/Artists Studio

But don’t expect a big reveal as to the back story of Anderson’s enigmatic DS Gibson. “There are a small handful of scenes, moments where you you understand her a little bit more,” she said. “If it were more than that, I would be disappointed.”

The BBC is clamping down on spoilers ahead of its transmission, expected in November, but Cubitt said he “wasn’t giving anything away” by flagging up the “growing obsession” between the hunter and the hunted.

“That’s the way of these investigations, particularly the multiple murderer, the police become increasingly immersed in their world, their psychology, in the hope of gaining the upper hand, some kind of insight, to stop them what they are doing,” he said.

Cubitt said he had not toned down the show in response to complaints about the on-screen violence against women – “There was some criticism but by no means a majority of people or anything of that sort” – but admitted: “My mantra during the first season as we should neither sanitise nor sensationalise Spector. That is a very difficult line to walk.”

Its return rises or falls on a moment, midway through the first episode, in which Spector’s character takes hiding in plain sight to a whole new level. Ingenious or incredible, it will either have you gasping – like much of the preview audience – or leave you pondering the decline of The Fall.