What’s a good psychological thriller without a lead detective with secrets of their own? That’s the question after episode three of ITV’s Scots-noir series The Dark. We’re also left wondering what skeletons DI Monica Kennedy (Laura Donnelly) has in her closet — and exactly how she ended up in a cult.

The small Highland community has been rocked by the murders of two young men. Kennedy and her partner, DCI Connor Crawford (Mark Rowley), found both bodies in the same ritualistic set-up, confirming that a serial killer is responsible for both murders. By episode two, it looked as though we had our first nailed-on suspect: Owen (Jack Hesketh), who has already murdered a man (it was later revealed that he was on drugs and thought the man was the devil, but still) and is being protected by his misguided mum.

But it’s not that simple. Owen is just another red herring in this gothic tale — and we’ve still got half the series to go, after all. With Owen critically injured in hospital — but, crucially, alive — Kennedy and Crawford find the taxidermied rabbit he was given. Handily, it contains photographs of the killer’s targets, including the latest target: the wayward Zandy (Charlie Geany).

The problem with being a small-time drug dealer is that when the police ask Zandy’s headmaster — also Tammy’s dad — to keep him there because he’s next on a serial killer’s “to-do” list, Zandy assumes he’s in trouble and bolts. When another pair of hapless cops try to collar him, he flees again, only for Kennedy to catch him back at home. He reveals that, yes, he was targeted by the killer, but he didn’t fall victim to his grooming. “Why would I get into a chat with a paedo?” he asks. Well, quite.

Meanwhile, more potential victims and suspects are being lined up. James (Anders Hayward), a colleague of social worker Michael (Tunji Kasim), acts incredibly shiftily when asked to pull up Zandy’s details. Surely asking to use Michael’s computer rather than his own is a red flag? He looks even more suspicious when he turns up as the psychologist treating Kennedy’s young daughter, Lucy, who has been parroting the autopsy findings to her schoolmates. Is this just a coincidence? Is James connected to the murderer or the mysterious Burning Light cult that keeps being mentioned? Is he linked in some way to Lucy’s dad? Or is it some combination of the three?

During an enigmatic in-car chat with one of her superiors, we learn that Kennedy was “brainwashed” into joining the cult after investigating it, and that her baby daddy may be a member, too.

“Last time you crossed paths with these nutjobs, they brainwashed you into joining them,” her cashew-munching colleague unceremoniously reminds her. That explains why Kennedy got so shirty with Crawford when he essentially asked how people could be so dumb as to join a cult. Her colleague also reveals that a “fucking admin oversight” meant the force hadn’t registered that “they moved them to the Isle of Mull about a month ago”. Then comes the strongest hint yet that Lucy’s father is someone in the cult (the leader?): Kennedy is told the move is “a good thing…he’s further away from Lucy”.

We may finally have a name for the red-haired woman who keeps harassing Lucy — and tried to kidnap her: Philly. She is likely part of the cult, too, and seems to have been brainwashed by the same man into believing Kennedy is a bad person and that Lucy should be taken from her. Here’s hoping the slap from Kennedy’s mum is enough to ward her off, but we need the full story of Philly, Kennedy and their links to the cult ASAP.

Meanwhile, Bethany Morgan (Helen Baxendale) gets the shock of her life when her son, Nichol Morgan, turns up very much alive on her doorstep, having been missing and presumed murdered. “Hey mother,” he says, weirdly. Has he had dealings with the cult, too? Maybe. But this definitely changes his status from victim to suspect.

Hopefully, we’ll learn more in the next episode. In the meantime, just as Kennedy suspected, the killer is striking again. His latest target is another teenage boy, Scott McKay (Liam King), who works alongside Don Cameron, the local hunter. Scott’s photograph wasn’t inside the stuffed rabbit. When the masked man turns up in Scott’s house, the darkness descends again…