Alejandro Landes’ mesmerising thriller Monos begins on a remote mountaintop where eight kids spend their time playing football blindfolded, dancing around bonfires, eating magic mushrooms and enjoying sexual freedom. The group resembles some kind of lawless scout group – or at least might, were it not for the strict training regime and machine guns slung from their shoulders.

These are the Monos, a guerrilla unit under the control of ‘The Organisation’; the setting is presumably Columbia, but we never find out anything about this shady group nor the surrounding political situation. The teens are left mostly to their own devices, save for occasional visits from a diminutive drill instructor known as The Messenger (Wilson Salazar), who tasks them with looking after an American hostage, ‘Doctora’ (an emaciated Julianne Nicholson) and a loaned dairy cow called Shakira.

Courtesy of Picturehouse Entertainment.

It’s a totally bizarre setup, immediately made more jarring by the presence of former Disney star Moisés Arias (AKA Hannah Montana’s Rico) in the terrifying role of unhinged child soldier Bigfoot. He’s joined by Wolf, Lady, Swede, Dog, Smurf, Boom Boom and Rambo (Sofía Buenaventura), the most sensitive, androgynous member of the group who emerges as a sort of protagonist.

In terms of raw audio-visual experience, you’ll struggle to find a better film released this year than Monos. Jasper Wolf’s cinematography is often abstract, always richly textured, and delightfully subjective, as is fitting for a film whose focus is in constant flux. Wide shots of the Monos silhouetted against and walled-in by vast, blue-hued clouds are genuinely breath-taking.

Then there’s Mica Levi’s elemental score – a mix of synth whistles, stuttered strings, rolling thunder and something best described as an alien helicopter sound – which proves essential to the film’s otherworldly atmosphere. It is nothing short of incredible; and, with just three film scores under her belt – Under the Skin and Jackie are the others – Levi has proven herself as the most interesting composer working in film.

Courtesy of Picturehouse Entertainment.

When outside conflict breaches the Monos’ isolated existence and forces them to relocate from their castle in the sky to the sweltering jungle below, there’s a worry that the film will lose the surreal edge of its first act. Writer-director Alejandro Landes, however, uses the shift in setting to brilliantly up the stakes. The dissolving group begins to turn against itself as they drift closer to something resembling the outside world, and it’s here the film’s immersive world becomes exhilarating – then positively terrifying – for a delirious finale.

Critics have been keen to point out Landes’ influences: the setup riffs on Lord of the Flies, the immensely physical military training scenes echo Beau Travail, the jungle madness feels like Aguirre, the Wrath of God or Apocalypse Now. All true – but that shouldn’t distract from the remarkable originality of this brilliant, bonkers film.

Monos is out in UK cinemas 25 October.