When the disturbed teen Matthew (Treadaway) comes home from hospital to live with his father (Wise), the tension is sharp enough to cut with a knife. And neither wants to talk to their care worker (Jennings). Both are still stunned by the disappearance of younger brother Tom (Palmer), who Matthew starts to see and hear around the grim London estate where they live. His best pal (Felton) thinks he's nuts, but a shy neighbour (Leeming) offers an understanding ear. And as more strange things happen, Matthew starts to lose focus on reality.

Director-cowriter Kevorkian has a great eye for unsettling imagery, using shadowy cinematography to capture the luridly decorated settings, plus a deeply jarring sound mix that keeps us off balance. The whole film feels like a nightmare, as we are pulled into Matthew's tortured mind. And Treadaway manages to subtly add texture to the character, even when the script seems to skim over the surface.

The problem is that nothing much seems to be happening until the plot groans into gear at the end. This is a thriller that moves at a snail's pace, focussing on psychological torment while hinting that something surreal or supernatural is at work. There are some great jolting moments here and there, and a terrifically emotional undercurrent, but the dialog and plotting are so simplistic and wilfully vague that in the end the film feels like an experiment in atmosphere rather than an actual thriller.

The scriptwriters also indulge in some rather hackneyed turns as the events unfold and we finally begin to learn what's going on (it's not a big surprise). The film as a whole has a tone that's as dry and cold as the people around Matthew, even as the undercurrent of raw tragedy constantly gurgles just out of sight. But it's worth seeing for Treadaway's emotive performance. And the skilful use of imagery and sound mark Kevorkian as a filmmaker to watch.

Sean (Pearson) is a 16-year-old living with his big sister Alice (White) in New Town, Edinburgh. After discovering that Alice is in debt to a ruthless loan shark, he accepts an invitation from the mysterious Alistair (Scott) to play a game, at the end of which Alice's debts would be paid. Meanwhile, Alistair has recruited Jamie (Mackenzie) to assist him. Over the course of one long night, Sean must outwit these two murderous men in order to save his life and his sister.

The main problem is that there isn't a discernible point to any of this. The narrative seems made up as it goes along, just throwing both Sean and Jamie into increasingly horrific situations that force them to do unthinkable things. Sure, they grapple with their consciences, but not meaningfully. For example, Sean considers joining his pal (Mnene) as an escort to make money, but gets right to the moment of truth before being repulsed; and Jamie is horrified by Alistair's brutality, yet only takes a stand when the violence turns against a woman.

Such a simplistic approach to morality leaves us with nothing to think about. And there's no subtext to Alistair's cruelty: he's only evil because Jobson wrote him that way. In fact, everything about the film feels similarly gratuitous, straining to develop tension through flashy editing and a harsh sound mix rather than characters or situations we can identify with.

The actors all dive headlong into their roles, and the fact that they are so emotionally present helps keep us watching, even though the characters are almost pathologically stupid. Sean in particular seems unable to make even the most glaringly obvious connections, and he also keeps dropping vitally important items as he runs. Which only emphasises how the plot relies so heavily on coincidences and contrivances. By keeping things so vague and undefined, Jobson creates a stylish sense of intrigue, but it's a shame he has nowhere to go.

When his mother (Simmons) falls ill, Robert (Wilby) heads home to the rambling family mansion near the sea with his teen kids Sam and Kate (Marlow and Lovibond). There they meet Mum's new mysterious friend, the young Joe (Dornan), who lives in a grounded boat in the marshlands. All of them fall under Joe's spell, with Sam following him around like a puppy and Kate flirting shamelessly. But Robert expresses deep disapproval and suspicion of Joe's friendship with his mother and his children.

Wilby is so good at playing the pinched, middle-class boor that we don't like him at all. Even his moments of smiling joviality are tinged with petulance. Robert is only play-acting the loyal son role for everyone around him; he's incapable of actual happiness. And once we get to know his mother, who's beautifully played by Simmons, we wonder how this could have happened, because she's as a feisty, life-loving poet and writer. We also wonder how Robert's children could be this curious and adventurous with him as a dad.

In other words, there are clearly some autobiographical elements here. The story is told from Sam's perspective, which means that Robert's relentless spitefulness is basically the screenwriter's daddy issue. And it doesn't help that the film piles on stereotypes, with everything marking this as a Serious British Period Drama--sundrenched photography, attention to 1970s detail, heavy-sounding dialog that doesn't actually say anything. Most conversations end with someone making a bold declaration then storming from the room before anyone can reply.

The film's jarring pace is also a problem, as the plot lurches past events, leaving us to wonder what actually happened. And some of what's on screen looks ridiculous (such as when one character nearly drowns in about six inches of water). But no matter how good the cast is, Rocksavage seems determined to make us despise Robert. We never feel even a hint of empathy towards him. Which makes the film feel more like a childish rant than a proper movie we can engage with.

A group of lively teens decide to skip school, causing trouble all over town and heading into the woods, where they run into a strange man, Peter (Howarth). He decides to teach these kids a few "valuable lessons" about pushing people around. When he challenges the kids to hurt him, things start to get creepy. And his wild mood swings freak them out even more than the pellet gun he produces. Eventually, the kids are cowering in fear, as Peter humiliates, terrorises and sometimes soothes them.

The film's freeform structure darts through the events without a story arc, which means we have no idea what could possibly happen next. This builds suspense as we follow the teens from energetic mischief to minor lawbreaking to tense confrontations with outsiders and each other. The young cast members are thoroughly believable, bringing intelligence and a primal quality to their roles. And Howarth is eerily convincing as the unhinged man who knocks the bravado out of them.

The filmmakers continually reference other movies, from Peter's mysterious Rambo-like past to the way the events will alter their lives as a group, Stand by Me-style. It also feels intriguingly like the inverse of last year's British horror Eden Lake, this time with the grown-up menacing the teenage tearaways. All of these points of resonance, plus sharply realistic dialog, help make the film gripping and often quite scary, even though there never really seems to be a point to it.

Is this about how easy it is to reduce people to their basest instincts? The situation brings out the worst in most of them, and they're clearly terrified of what they're capable of doing. But the fact that one boy (Conway) is confined to a wheelchair seems to be less a comment than a gimmick. In other words, this is essentially an exercise in atmosphere, with gloomy woods, social-issue overtones and a man who could snap at any moment. And once we realise this, it kind of loses its grip on us.