 In 1973, in Santiago of Chile of the first socialist president democratically elected in a Latin-American country, President Salvador Allende, the principal of the Saint Patrick School, Father McEnroe (Ernesto Malbran) makes a trial of integration between students of the upper and lower classes. The bourgeois boy Gonzalo Infante (Matías Quer) and the boy from the slum Pedro Machuca (Ariel Mateluna) become great friends, while the conflicts on the streets leads Chile to the bloody and repressive military coup of General Augusto Pinochet on 11 September 1973, changing definitely their lives, their relationship and their country.