Jonathas lives with his parents and his brother, Juliano, in a cottage in a rural area of the Amazon. The family harvests and sells local products at a roadside fruit stand, a place of contact with new friends and novelties from the rest of the world. They meet Milly, a visitor from Ukraine, and the native Kedassere. The group decides to spend the weekend at a campground in the jungle. Against his father's wishes, Jonathas will embark on this adventure. Seduced by Milly and the forest, he undertakes his most transforming journey.

In Luz nos trópicos, Paula Gaitán weaves together a dense fabric of storylines, timelines and settings, intermingled with indigenous cosmologies, travelogues and anthropological literature. Initially, the director follows a young man of indigenous origin. At the beginning, he is standing on the banks of the East River in winter. Soon he is travelling upriver through the Brazilian jungle to a village, where he is greeted like an old friend. In a second storyline, the director accompanies a group of European settlers. They are also travelling upriver, collecting, possessing and searching for a position from which they can survey the forest and the river. Some 150 years separate the two layers; sometimes, a dive into the water dissolves this separation in the space of a second. Later on, the film wanders northwards again and the layers collapse into one another. Between Walden Pond and the Amazon lies just a cut.
Luz nos trópicos is an homage to the abundant greenery of the Amazon region, the woods of New England in winter and the indigenous populations of both Americas. A film that is as free-flowing as a winding river.