This story, based on Peter Matthiessen's 1965 novel, is set in the Amazon rain forest where the Niaruna Indians are besieged by some supposedly civilized outsiders who want to save them. Two Protestant missionaries (John Lithgow and Aidan Quinn) hope they will give up their tribal ways and accept the Lord. A half-Cheyenne adventurer (Tom Berener) goes native in a messianic effort to prevent their extermination.

At Play in the Fields of the Lord is a thought-provoking film about cultural conflict, power, progress, and the dire consequences of messianic thinking. It was brought to the screen by producer Saul Zaentz who was also responsible for film versions of One Flew Over the Cuckoo's Nest, Amadeus, and The Unbearable Lightness of Being. He sees this drama as a study in "power, progress, greed, religion, and one man thinking he can change the world." It is also about the high price that indigenous peoples pay for being helped. It is also about compassion as a spiritual resource that can go a long way toward opening our hearts and minds to other people and places. The most troubling aspect of the movie is that the situations it depicts are still happening today.