Sonny Corpus, an orphan raised by poor relatives in the slums of Manila, spends his time with Celso, Jimmy and Rodel, his three best friends. But when Celso pressures Sonny to take part in a robbery, Rodel, Jimmy and an old woman are killed. While the guilty Celso flees, Sonny is arrested and charged with the woman's murder. Unable to prove his innocence or his status as a minor, Sonny is sentenced to death by lethal injection and confined to Manila's national prison, a naive boy in a jungle of hardened criminals. With his life seemingly beyond repair, Sonny meets two people who bring hope into his shattered existence. Lolo Sinat, a 70-year-old gang leader feared by the other inmates, takes Sonny under his wing, becoming his protector, teacher and saviour. Meanwhile, Gina, an alcoholic attorney, is assigned to investigate the legitimacy of Sonny's imprisonment. Together, they enlighten Sonny as to the ways of the law and the law of the jungle.