15-year-old Rufino roams the streets of Mexico City, trying his best to look after the youngest homeless children who survive on a diet of glue and hash and sleep in the sewers. He earns some money doing hard, dirty work, such as moving meat around a slaughterhouse. When he sells a bag of cocaine for Ochoa, a corrupt cop who has Rufino's district in his power and is also the lover of Rufino's adoptive mother, Rufino decides to use the money to flee the city with his girlfriend and their baby--and Ochoa sets off after them. About to escape, Rufino finds out that his real father is still alive; obsessed by this knowledge, he doesn't want to leave until he finds his father.