I'm Gonna Explode (Voy a Explotar), Gerardo Naranjo, 106 mins, (15)

This Mexican 'Badlands' is a joy, until the bloody ending leaves a sour taste

(Imagenet)

Roman (Juan Pablo de Santiago) is a problem Mexican teenager. You can tell by little giveaway moments.

He keeps a diary minutely itemising the sequence of events on the day he will blow the brains out of the priests at his high school. He contributes to the school drama evening a sketch called "See you in Hell" in which he hangs himself on stage. He has to pay an associate to pretend to be his friend. His father, a corrupt bigshot politician, has absconded with his foxy secretary, and Roman has been raised by a hirsute, intellectual friend of the family, leaving him simultaneously feckless, foul-mouthed and desperate for love.

Maru Hernandez (Maria Deschamps) is also a piece of work, a 15-year-old contrarian, who spends nights sleeping in a van with someone she can't stand, drinks whisky, hates her mother (whose husband has left home) and keeps a running commentary in her head that's aching with romance. When they meet, Roman persuades Maru to get herself expelled from school and go with him in search of a big adventure.

Gerardo Naranjo's third feature comes with an incalculably cool endorsement: among its many executive producers are Gael Garcia Bernal and Diego Luna, the real-life childhood best buddies who played the teenage best buddies Julio and Tenoch on a road trip with a 20-something woman in Y Tu Mama Tambien, a landmark in Mexican cinema. When you learn that Naranjo was himself a teenage rebel in his native Salamanca, and that he founded a cinema club at a university named after Zéro de Conduite, Jean Vigo's small masterpiece of schoolboy rebellion, it's not surprising to find his film is about youngsters on the lam. What's unusual is the way the film avoids many clichés of the Misunderstood Kids genre.

The naive voiceover was all-but-patented by Terrence Mallick in Badlands, in which Sissy Spacek confided her belief that her psychopath co-fugitive boyfriend (Martin Sheen) was just a highly strung romantic. The desperate couple legging it from the big city brings Godard's Pierrot le Fou to mind. But Roman and Maru don't go in for extremes. They don't go anywhere. When technically on the run, they set up home on the roof terrace of Roman's parents, in order to spy on the bourgeois hysteria their actions have generated. They break in and steal home comforts, while the elder generation sleeps off their tequila. One kid hides behind the family sofa as the parents watch a documentary about kidnapped children. There's a nice contrast between the strained conversation of both sets of parents as they discuss the plight of their offspring (murkily filmed on videocam) and the joy of freedom on the roof (filmed in sunlit colour) as the teens drink wine, barbecue food and fumble towards having sex. They don't seem like crazy rebels, more like embracers of an alternative lifestyle.

Also, they don't rob and kill people. Unlike most kids-on-the-run movies, from A bout de souffle to Bonnie and Clyde, Roman and Maru don't slaughter strangers or waste cops. They merely explore each other. But when, late in the film, they acquire a gun, you know one of them has had it. Especially after a lush little slo-mo episode when Maru intones her belief that life is about discovering "something to fight for, something to live for ... a twin ... a perfect accomplice" – words heavy with irony and freighted with doom.

Naranjo's direction impresses most in the first reel, when he captures the chaos of Roman's mind through split-second intercutting. The convergence of the young leads is nicely handled too, as they lie around on a diving board and she asks, "What do you see me as? As a girl, or as me?" The feeling that they are each other's constructed love object is ever-present: there's always someone writing a journal, acting on stage, seeing the world through a lens. "Like a story we used to make up, a boy appeared," breathes Maru on first seeing Roman, "and everything changed."

The climax sees the runaway pair actually running at last, attending a birthday party, acquiring a dog and wondering about fleeing to Mexico City. Maru wears a grown-up white frock and looks like a bride, while Roman embraces the grown-up world by getting drunk and aggressive. The scenes that show this game-but-dysfunctional little family emerging into adulthood are genuinely moving. The blood-drenched ending may leave you with a sour taste in the mouth, but you'll remember the performances with pleasure – darkly handsome Juan Pablo de Santiago is a fine aspirant tough guy and hopeless lover, and Maria Deschamps is a knockout as Maru, her sparkling brown eyes radiating independence, intelligence and desperate need. I'm Gonna Explode never quite explodes but it sets up a potent, sometimes funny, opposition between domestic complacency and youthful rejection, and a slow-burning love story that draws you in. It establishes Gerardo Naranjo right up there with Alfonso Cuaron as a jalapeño-sharp master of Mexican realismo.

Tips for 2010

By Jonathan Romney

I am love: The renaissance in Italian cinema has given us Gomorrah and Il Divo. Now it steams into stranger waters with this magnificent melodrama by Luca Guadagnino. It's the story of a wealthy Milanese dynasty and a woman (Tilda Swinton) who has married into it – and who finds that passion may be her way out of it. Opulent and austere, I Am Love is a bravura piece with echoes of Visconti and Antonioni.

Shutter Island: Martin Scorsese's delayed retro-thriller stars the newly jowly Leonardo DiCaprio as a cop investigating a murder in a secluded mental hospital. It's based on a Dennis Lehane novel and looks labyrinthine and very gothic.

Dogtooth: An intensely strange film by Greek director Giorgos Lanthimos and a must for fans of the unhappy-families films of Michael Haneke. Three grown-up siblings have lived their lives locked into their home by their parents, apparently as part of a bizarre language experiment. Surreal and disturbingly erotic, a black comedy in the Buñuel vein.

Face to Watch:

French actress Sylvie Testud is one of the best-kept secrets of European cinema, who had her first moment of glory as a working-class housewife in the Dunkirk-set drama Karnaval (1999). She's since turned up in Piaf-biopic La Vie en Rose and starred in a 2008 biopic of Françoise Sagan. So why Testud in 2010? Because of her lead role in Jessica Hausner's stylishly unsettling drama Lourdes, in which Testud gives a superb performance from the less-is-more school.