Based on actual events, previously covered in the 2002 documentary 'Bus 174', this gritty drama traces the events and circumstances that led to an armed siege on a Rio bus in June 2000. After her baby son Allessandro is kidnapped by a drug gang to whom she owes a debt, reformed drug addict Marisa (Chris Vianna) spends her time scouring the juvenile detention homes in search of her son. Meanwhile, in another part of Rio, Sandro do Nascimento (Vitor Carvalho), a young homeless boy, arrives at his mother's shop to find her brutally murdered. After running away and falling in with a group of street kids, Sandro becomes a drug addict, narrowly managing to survive the 1993 massacre of homeless children at Candelaria. When he is sent to a juveline detention centre, he is found by Mariso, who mistakes him for her lost son Alessandro, and takes him into her care. But despite Marisa's best efforts, the now adult Sandro (Michel Gomes)'s despair soon leads him to take a busload of passengers hostage.