The film is about a group of destitute children and their misfortunes in a Mexico City slum. El Jaibo escapes juvenile jail and reunites with the street gang that he leads. They attempt to rob a blind street musician and, failing at first, later track him down, beat him, and destroy his instruments.
With the help of Pedro, El Jaibo tracks down Julián, the youngster who supposedly sent him to jail. El Jaibo puts his unharmed arm in a sling, hides a rock in it and confronts Julián, who denies that he reported him to the police and refuses to fight El Jaibo because it would not be a fair fight. As Julián starts to walk away, El Jaibo hits him in the back of the head with the rock. He then beats Julián heavily with a stick and takes his money, killing him. El Jaibo warns Pedro not to report the crime and shares Julián's money with Pedro to make him an accomplice.
Alfonso Mejía as Pedro (right, behind) in a publicity photo for the filmPedro's mother resents her son's behavior, and shows that she doesn't love or care for him. Pedro is saddened by this, vows to start behaving better and finds work as apprentice to a blacksmith. One day, El Jaibo comes to talk with him about their secret and, unbeknownst to Pedro, steals a customer's knife from the blacksmith's table. Pedro is accused of the crime and sent to a juvenile rehabilitation program, the "farm school", where he gets into a fight and kills two chickens. The principal tests Pedro by handing Pedro a 50 pesos bill to run errands with. Pedro accepts and leaves with the intention to complete the errands. As soon as he leaves, he encounters El Jaibo, who steals the money. Upset that his attempt to be good was foiled again, Pedro tracks down El Jaibo and fights him. The fight ends in a stalemate, but Pedro announces to the crowd that it was El Jaibo who killed Julián. El Jaibo flees, but the blind man has heard the accusation and tells the police.
Pedro tracks El Jaibo down once again to murder him. El Jaibo kills Pedro. While fleeing, El Jaibo encounters the police and, as he tries to run away, the police shoot and kill him. Meche and her grandfather find Pedro's body in their shed. Not wanting to get involved, they dump his body down a garbage-covered cliff. On their way, they pass Pedro's mother, who, though once unconcerned with her disobedient child, is now searching for him.
