Julio and Tenoch (García Bernal and Luna) are old mates - well, as old as their 17 years allow. Hanging out at a ritzy society wedding they try out some moves on the gorgeous, 28-year-old, unhappily married Luisa (Verdú). To their surprise, within days the two of them are escorting their catch out of Mexico City in search of the legendary perfect beach, Boca del Cielo ('Heaven's Mouth'). For most of the movie Luisa is in the metaphorical driving seat - when things get sticky she's quick to lay down the law. Meanwhile the guys' machismo is the butt of most of the jokes; in particular, their competitive and possessive instincts, which Luisa does her best to cure. The film's frank, uninhibited sex is refreshing, funny and true - but there's more. Divesting themselves of all the artifice and affectation, the green-tinted spectacle of their two Hollywood productions, Great Expectations and A Little Princess, Cuarón and cameraman Lubezki get their hands dirty here, for a more crisp, direct, objective approach. One side-effect is the trenchant, rueful portrait of Mexico which emerges on the margins: the vast disparities between rural and urban standards of living, old and new world cultures.