Von Martius is a geologist and amateur filmmaker who joins two local documentarists in their journey to a cave complex called Caverna da Lua (Cave of the Moon), near the small town of Luminárias in Brazil. Upon their arrival they learn about an ancient indigenous legend regarding the cave and the strange, eerie lights that have been reported in the region for hundreds of years.

In his search for the cave, Von Martius finds himself persecuted by the local military, venturing alone into the wilderness and experiencing mysterious luminescent events for which he has no explanation: all leading him to a transforming experience once he reaches his final destination.