EDEN LAKE

IF YOU go down to the woods today, you're sure of a big surprise, according to The Teddy Bears' Picnic. In horror-thrillers that surprise is invariably a terrifying fate, as experienced most recently by the unhappy couple at a US woodland retreat in The Strangers.

This week's victims are a loving couple, Steve and Jenny, played with convincing chemistry by Michael Fassbender and Kelly Reilly in Eden Lake. This English thriller opens on a scene of sweetness and light, at the school where Jenny teaches angelic young girls. Those are the only positive images of children that will feature in this movie.

The couple take off on a romantic camping weekend by a secluded lake on the edge of a woodland area. Spending the first night at a small hotel, they are whispering sweet nothings to each other when they're interrupted by a noisy boy, who promptly gets a hard slap from a parent. There's another bad omen the next morning, when they discover their idyllic retreat is under construction for a housing project. Tampering with nature is never a good sign, even as a backdrop, in a modern movie.

It gets worse. Relaxing on the beach, Steve and Jenny are harassed by five boys and a girl who are in their early-to-mid teens and fuelled with as much mindless aggression as the creepy adult locals in Straw Dogs. The conflict escalates overnight as the amoral nature of the teens, which explicitly recalls Lord of the Flies, is encouraged by their callous, sadistic 16-year-old leader (Jack O'Connell).

Evil is an equal opportunity measure in this scenario, and the hard-faced girl in the gang (Finn Atkins) evidently takes pleasure in filming their brutality on her phone. One would rightly be tempted to blame the parents, and there is good reason when we meet them.

As Eden Lakeunflinchingly reveals the capacity for malevolent, mindless violence in adolescents, it taps into concerns over youth violence here and in Britain.

Writer-director James Watkins takes a bleak, despairing view of contemporary society in his taut, keenly paced and deliberately disturbing film, which pulls no punches in graphically depicting gory torture. This cautionary tale is, unusually for a horror-thriller, rooted in realism, even though one of the protagonists makes mistakes common to so many characters in this genre - without which the film would be over in half an hour.