When Marisa is unable to pay a debt, her baby, Alessandro, is taken away from her by a drug dealer. After cleaning up her act, she becomes determined to find her child. On the outskirts of Rio, another boy, Sandro, finds his mother stabbed to death in her shop. He runs away, intent on reaching Copacabana, where his mother once promised to take him.
Once there, Sandro befriends some street kids who sweep him up into a world of drug use and dealing. After becoming a hardened survivor of the Candelaria massacre (an attempt by Rio police to clean up the city by murdering street kids as they slept), he eventually finds himself in a juvenile detention home.
It is there that he meets Marisa's long-lost boy, Alessandro. Marisa meanwhile finds her way to the center, and mistakes Sandro for her own son. Despite her efforts to help him, Sandro cannot escape his hard reality, and ultimately becomes the hostage-taker on Bus 174.