The film evokes the stay in Brazil of Claude Levi-Strauss, an ethnologist, who stayed there from 1934 to 1938. His stay gave rise to the book "Tristes Tropiques". Based on images taken in 1935 and today, his statements reconstruct his intellectual journey in the field of ethnology. Searching for primitive worlds, he tried to understand the Indians whose decaying societies offered an "essence of social life." The work gives us an account of the importance of this scientific and philosophical expedition.