The story centers on Tsotsi (meaning thug), an adolescent in Soweto, the shantytown slum of modern Johannesburg, South Africa.  There Tsotsi (Presley Chweneyagai) leads a loose-knit gang of menacing thugs.  When gang members are first encountered, Butcher reveals his disturbing and sinister nature; Boston (Mothusi Magano), except for his alcoholism, represents a potentially thoughtful but ineffective source of goodness and decency; Aap (Kenneth Nkosi), a simpleton, is devoted to Tsotsi; and Tsotsi seethes with, as yet, inexplicable rage. 

As the story unfolds, a petty crime leads to senseless murder and an old wheelchair-bound man is threatened and cruelly abused.  Finally, Tsotsi, without gang participation, shoots a woman during an auto theft.  When he drives recklessly away, he discovers an infant in the stolen car's backseat.  Rather than killing the baby, his first inclination, he puts it into a paper bag and takes the baby home.  This new relationship--and responsibility becomes the harrowing twist in the story.   

Throughout, short and disturbing flash backs of Tsotsi's childhood reveal unimagined beginnings that have led to the boy's simmering rage and the string of unforgiving actions.  While concerns about vulnerable children within a context of social injustices are foremost in the minds of film viewers, the overwhelming circumstances and complexities frustrate thoughts about realistic interventions.