A romantic weekend by the lake turns into a terrifying ordeal for Jenny (Kelly Reilly) and Steve (Michael Fassbender) when they confront a mob of vicious local tearaways. Frequently crossing the pain threshold, James Watkins' blood-drenched survival thriller is a grim reflection of a society where teenage kicks can become a matter of life or death. This Is England's Thomas Turgoose goes delinquent once again.
If you're someone who'd rather wait an hour in the rain than board a bus carrying more than one teenager, it's unlikely this contemporary spin on Lord of the Flies will have you rushing out to hug the nearest hoodie.
Having written lean, mean psycho-thrillers My Little Eye and Gone, James Watkins has form when it comes to delivering chills on a budget. Unsurprisingly, he sticks with the devil he knows for his first, er, stab at directing.
It's also a devil we're reasonably familiar with: unsuspecting townies cross blood-crazed yokels with progressively icky results.
Intending to pop the question to Jenny (Reilly), Steve (Fassbender) loads up the Jeep and whisks her off to a divers' paradise somewhere in the wilderness north of Watford Gap.
After an uncomfortable night at the local village pub (which couldn't be less welcoming if it had Brian Glover telling jokes about Mexicans and werewolves roaming outside), they find that the bulldozers are about to transform Eden Lake into a yuppie eyesore.
But for now it's a lovely spot... until a bunch of nasty little yobs turn up on their BMXs with a cheap stereo, a few alcopops and a dirty great Rottweiler (the only living thing they don't torment). Steve words them up. They diss him - and his woman.
Next day, matters begin to get out of hand when the kids steal the Jeep and Steve accidentally kills their dog. In the ensuing pursuit, Jenny escapes but Steve is trapped. Then fings get well bad.
Commanded by sadistic Brett (Jack O'Connell), the so-squalid crew truss their captive in barbed wire and take it in turns to cut him to ribbons. Traumatised, Jenny gives her hiding place away and runs for her life - and Steve's too.
Poor Kelly Reilly - she really goes through the grinder as the freckly, flowery schoolteacher we first meet disappears under layer upon layer of mud, crud and blood. Mind your foot on that metal spike! Too late...
Watkins maintains the intensity of the hunt throughout. Not long ago, the kids' pack mentality and sheer barbarism would have seemed implausible. Nowadays, such behaviour is less easy to dismiss.