Monos

There are direct nods to Lord Of The Flies in Alejandro Landes' Monos - not least a pig's head on a pole - but unlike William Golding's novel, Landes' nightmarish depiction of a group of child soldiers in the mountains and then forests of an unnamed and remote part of Latin America starts its descent into darkness from a place that is already fully feral.

A group of teenagers - shorn of their original identity and now going by one-word nicknames, including Wolf (Julián Giraldo), Lady (Karen Quintero) and Bigfoot (Moses Arias, who you might remember from The Kings Of Summer) - spend their days practising violent drills as they guard a kidnapped doctor (Julianne Nicholson) on a muddy mountaintop. We learn they are working for The Organization, a shadowy group represented by occasional radio orders and visits from a pint-size dictatorial commander named, appropriately, Mensajero (Messenger, played by Wilson Salazar). He arrives periodically to dish out some additional brutality and instructions and, near the start of the movie, to present them with a cow with the wonderfully surreal name of Shakira, who they are tasked with taking care of.

Spoiler alert: Taking care of things is not their forte.

Landes' film has the queasy, uneasy feel of a nightmare - and that's before magic mushrooms are involved. We're not exactly sure how any of these kids got here but we know they're in hell now, relying on ritual and force to keep one another in line. Equally, we don't fully understand why they're imprisoning the doctor, but we are, as we might be in the middle of a fitful sleep, mainlined to her fear and desperation. When things go badly, as we know they must, Landes plunges the action into the jungle as the group begins to fracture - with scenes that look so dangerous you wonder how on earth they kept the cast from harm. All the while composer Mica Levi performs the same musical magic trick she did in Marjorie Prime and the rest of her back catalogue of building tension so subtly you barely notice the score until she decides to bang you right across the head with it with concussive force. She's one of a handful of composers working today who its worth going to the cinema just to listen to.

The nightmare feel extends to the plot, which is deliberately fragmented and the cinematography from Jasper Wolf, which mimics the unpredictability of the youngsters, often sweeping in for disorienting close-ups. Some of the action hinges on conflict between the androgynous Rambo (Sofia Buenaventura) and increasingly unhinged Dog (Paul Cubides) but the story jumps unsettlingly but effectively from character to character as factions and allegiances form and break. A dark allegorical nod to what happens to children in political turbulence? Perhaps, but Landes' main focus is on drilling these chaotic kids' and captive's emotions into us so deep they may well emerge later in your own nightmares.