Mexican teenagers Tenoch (Diego Luna) and Julio (Gael Bernal) are friends as close as brothers. When their girlfriends decamp to 'do Europe' for the summer, they decide to dedicate their time to the pursuit of sex and partying. At a wedding reception they cross paths with Luisa (Maribel Verdu) a young woman in her twenties but older than both boys. Immediately taken with her they invite her to take a roadtrip with them to an invented beach called 'Boca del Cielo' (Heaven's Mouth). Luisa declines but when a call from her husband confirms that he has been cheating on her, Luisa decides to take the boys up on their offer. As the trip is undertaken all three learn a lot about each other, not always happily, not always expected.