Jeremy Irons appears as Father Gabriel, a Jesuit priest who enters the South American rainforest with the intention of building a Christian mission. His challenging task is the conversion of a small tribe of native Amazonian Indians. Although it is slow going, Father Gabriel and his small group of Jesuits gradually succeed in befriending the natives, learning about the Indians' culture and language along the way. Gaining their trust, Father Gabriel is able to teach his new friends about his faith.
In the meantime, Spanish army officer turned slave trader Rodrico Mendoza (Robert De Niro) is part of the thriving South American slave business. Mendoza is caught up in a tragic love triangle – he is in love with a woman who only has eyes for his younger brother. When she confesses her passion to Mendoza, he flies into a jealous rage, eventually murdering his own brother. Stricken by grief and remorse, Mendoza is saved by Father Gabriel's guidance, and joins him in his mission. Here Mendoza finds peace and seeks to become a priest. However, this idyllic life is not going to last. When Spain sells the land to Portugal, Mendoza and Father Gabriel must find a way to protect both the mission and the Indians from the aggressive Portuguese, but they have very different ideas on how to go about it.
This fine film is often unfairly overlooked, as its good features significantly outweigh the bad. The story is based on real events, and the film rarely strays from telling the unembellished truth. The movie looks wonderful, with fabulous scenery shown off through outstanding cinematography. Robert De Niro and Jeremy Irons both turn in intense and convincing performances, supported by a cast that includes genuine Guarani Indians – descendants of those who experienced these events for real. Thoughtful, touching and with great emotional depth, the film makes its case without descending into sentimentality or clichés. That being said, the plot is sometimes not easy to follow and tends to meander during the middle of the story.