It's Halloween 1997, and skater-gang leader Jango (Holborow) unleashes a torrent of abuse on a lonely gay kid. But skater and aspiring photographer Corey (Wallace) is horrified by this bullying and Jango's philosophy that "if you want to run with the wolves you've got to kill a few lambs". Later, Corey leaves the wolfpack at their party in the cemetery. In town, he runs into the outcast Jonah (McGrath), who reminds him of the games they used to play together as young boys (Barry and Winta McGrath). Meanwhile, Jango decides to take the pack hunting.

The film has a driving sense of energy, with emotions ready to explode at any moment. As Corey and Jonah take an imaginative journey together, the film evokes fantastical-horror undertones that become truly frightening on a very personal level. Scenes are colourful and visceral, depicting the best and worst of human society. Verso cleverly merges the past and present using skilful camerawork, editing, lighting and effects. But he also loses some of the power by indulging in a bit too much fantasy and shying away from some key details.

Performances are raw and natural, bracingly playing up the bravado of teens who are trying to survive the pressure to be just like their friends. Wallace offers a terrific sense of Corey's conflicting inner feelings, understanding that he has taken sides out of a need to survive. McGrath's Jonah is fascinating kid, naturally charismatic, trying not to be cowed by abuse, making a daring attempt to reconnect with his old friend.

All of this is a bit swirly and dreamlike, with rather pointed observations about how childhood is lost as we grow up, turning us into people we barely recognise. As the lone female character (Ruhlmann) asks, "Why do girls grow up while boys act like idiots with their heads in the trees?" There are also some strong comments about the time and place, as the teen gang's vile homophobia is almost expected and encouraged. And of course the truth is that the real heroes are the marginalised ones who dare to stand up to the pack.

As he investigates a bizarre double murder, detective Chris (Meeten) is assisted by profiler Kathleen (Lowe) to go undercover to learn what psychotherapist Helen (Cusack) knows about her missing patient Coulson (Jones). But posing as a patient, Chris begins to lose his grip on reality. He befriends Coulson and imagines Kath as the woman he loves, even though she's settled down with his friend and colleague Jim (Skinner). Then Helen refers Chris to a seriously odd new therapist, Alex (McGivern). And Chris finds himself unable to remember which part of his life is authentic.

The misleading but clever title refers to Coulson as a person who is obsessed with lurking around crime scenes. And it of course also refers to whatever is haunting Chris' splintered consciousness. Tunley creates a vivid tonality throughout the movie, deploying a moody score (by Waen Shepherd) and observant cinematography (by Benjamin Pritchard) to maximum effect. The film is lush and often jarringly cyclical, with a witty sense of pace and darkly emotional undercurrents.

Each character is a bundle of textures and secrets, from silently obsessive to smug and talkative. People pop in and out of the story, creating tension and plot wrinkles, and continually throwing Chris off as he tries to work out who is whom in his personal and/or private life. Meeten is likeable and sympathetic in the role, surrounded by an excellent supporting cast. The always terrific Lowe, Skinner, Cusack and Kaye add plenty of surprises. While the scene-stealer is the quirky, suggestive McGivern.

As things get increasingly dreamlike, Tunley drops in references to mind-bending imagery like Mobius strips (unending loops), Klein bottles (inside and outside at the same time) and sigils (symbols that have magical power). The mix of supernatural overtones with mental issues is fascinating, even if it leaves the audience with less and less to hold on to. But by this point, we are so fully engulfed in Chris' psychological meltdown that we actually have an eerie understanding of how he feels.

In Newcastle, Dan (Johns) is a carpenter in his late 50s, recovering from a heart attack. His doctor tells him he shouldn't return to work quite yet, but the state's disability payment has been stopped by a private contractor, a "health professional" who thinks he looks perfectly fine. While he's forced to wait to appeal this cold-hearted decision, he meets young single mother Katie (Squires) and her two children (Shann and McKiernan), who are also caught out by new regulations that seem to have been created to make getting even a little assistance virtually impossible.

These are decent people just trying to survive in very difficult situations, but the rulebook keeps changing. And the workers in government offices are becoming increasingly rule-bound, seemingly unable to tap into even a hint of respect or compassion for the people they should be helping. To make matters worse, everything has shifted online, and Dan has zero experience with computers or smart-phones. He's more at home making furniture from scraps of hardwood and helping Katie get her new flat in working order.

Performances across the board are bracing for their honesty. No one seems to be acting at all, and both Johns and Squires are hugely likeable people who aren't remotely perfect but are well worth rooting for. Intriguing side roles include a lively, entrepreneurial neighbour (Sikazwe) and two job centre employees (Rutter and Percy) who take opposite approaches to their work. There's also a security guard (McGregor) who offers Katie a job she'd rather not do, but has little choice about.

Refreshingly, there isn't a villain here; sure, some people are more heartless than others, but it's the system that's to blame, specifically a Conservative government that has slashed services to ribbons so they are on the verge of failure, then blamed the problem on benefit scroungers. But the point is that these are human beings at their most vulnerable, navigating a nonsensical bureaucracy that not only wastes time and money but encourages both cruelty and desperation.

As Tom and Nicola (Riley and Froggatt) await the birth of their second child, Tom comes down with what seems like food poisoning. Except that it's actually sepsis. Most people die of the infection, but Tom survives. And while he's unconscious, Nicola has to make the difficult decision to remove the infected tissue, including his arms, legs, nose and mouth. When he wakes up, their young daughter Grace (Copping) doesn't know him. And their life becomes precarious because now Nicola can't return to work following the birth of their son.

The way this family falls through a crack in the British system is shocking. Tom needs more than the basic care provided through the National Health Service, and without an income they begin going under. They set up a fund to help with treatment, and while Tom's and Nicola's mothers (Dotrice and Nicholls) offer assistance, their involvement creates another kind of stress. The conflict here is earthy and honest, and much of it stems from recognisable emotions like pride and self-pity.

Riley beautifully evokes Tom's inner struggle to both acknowledge his new reality and rise above it. This isn't a simple challenge by any means, and the details of his treatment are fascinating, while the internal journey is wrenching. Froggatt has perhaps even more intense feelings to convey, as Nicola struggles against Tom's attitudes and her own thoughts. In many ways, she's the character the audience identifies with most intensely, and she helps us see things in ourselves we perhaps wish weren't there.

There are moments that get rather melodramatic, and some plot points feel over-egged. But the core story here is so vivid and resonant that it can't help but keep us both completely gripped and on the edge of our emotions all the way through. Of course, the scariest thing about this film is that sepsis is so little understood or reported, even though thousands die of it every year. Tom's story may be one of survival, but he travels a very tough road. And this family's tenacity is a real inspiration.