Explorer and naturalist Evrard Wendenbaum leads a team of scientists into the Matarombeo Massif, a limestone karst on the Indonesian island of Sulawesi so remote and tangled that no full biological survey of it has ever been completed. The film follows the expedition as it cuts through dense jungle, rappels into sinkholes, and navigates the massif's cave systems and razor-sharp rock formations to reach pockets of forest that may never have been studied. Along the way the team documents species found nowhere else, from tarsiers to rare orchids, while researchers catalog specimens on the spot to build what is billed as the area's first scientific inventory. Wendenbaum's approach favors hard physical access over armchair theorizing: the crew hauls gear up cliff faces and wades through flooded caverns, with the terrain itself acting as the main obstacle to the science. Interviews with the scientists explain what each find might mean for understanding the region's isolated ecosystem, and the footage of Sulawesi's hidden interior, shot at close range, carries most of the film's weight.