Tenoch e Julio são dois adolescentes de 17 anos que são controlados pelos seus hormônios e desejam se tornar adultos rapidamente. Em uma tarde festiva eles encontram Luisa, uma garota espanhola 11 anos mais velha que eles e que é casada com o primo de Tenoch. Eles a convidam para uma viagem à praia de Boca del Cielo, convite este inicialmente recusado e posteriormente aceito, após Luisa receber uma desagradável notícia. Porém, tanto Julio quanto Tenoch não conhecem o caminho até a praia e nem mesmo se ela realmente existe, fazendo com que os três se aventurem em uma viagem onde inocência, sexualidade e amizade irão colidir.
While recently watching "Blue Is the Warmest Color," I was reminded of this film, and like "Blue," I was drawn to how the film's central relationship between Tenoch and Julio felt both astoundingly ecstatic and yet isolating, especially when it ends. It's as if the passions from their road trip to Heaven's Mouth burned too brightly to be sustained once they returned to their normal lives. I first looked at this film as a coming-of-age film, albeit one that happened to include sex scenes much more graphic than others of its genre. That opinion helps me find a reflective starting point for this film, but every time I watch it, I think more and more about the socioeconomic points Cuarón interjects throughout. I think more about how little I know about other countries, especially the one just south of my own. (I suppose Tenoch and Julio don't know that much either.) After this last viewing, I thought more about whether the the two actually learned something positive from the experience. We're told they never meet again after the film ends. What happens next? And how does this trip I witnessed mean to that answer?