Our story begins with anthropologist Jake Higgins and his linguist wife Mia traveling deep into the Amazon jungle to find the uncontacted 'Yabahuaca' tribe. Their primary goal is to study the secrets of these isolated natives. Mia insists on making the first contact alone, leaving her gear at the camp and disappearing into the jungle. For the first few days, she communicates with Jake frequently via radio. However, on day 32, a terrifying scream echoes over the radio: Mia cries out that she is in danger, that the tribe is attacking her, and she is running. A panicked Jake rushes into the dark forest, only to be chased by tribal warriors. He falls off a cliff, loses his memory, and awakens to the terrifying isolation of the game.

Upon waking up, his only possession is a working radio. Mia is on the other end, but her voice sounds distant and strange. As Jake learns to survive from scratch, he discovers 'Ayahuasca' bowls abandoned by the tribe. Every time he drinks this concoction made from mystical Amazonian plants and dreams by the fire, a part of his memory returns. In his visions, he remembers that they had actually encountered the tribe before. He recalls that Mia had terminal cancer, and they had come to the jungle specifically to use the tribe’s miraculous healing abilities to unlock the secret that would save her.

Deep in the jungle, searching for clues, he stumbles upon massive abandoned technological research tents (Lambda 2). This area belongs to a giant Brazilian company called the Omolú Corporation. The company had provided massive funding to Jake, asking him to steal the Yabahuaca tribe's miraculous healing secrets. Jake realizes he’s not just an innocent researcher; he sold his soul to the company to save his dying wife and pay medical debts. In this camp, he reads logs revealing that the natives were forcibly used as guinea pigs, their blood harvested, and subjected to unimaginable torture. His mental state deteriorates by the hour.

During the final Ayahuasca sessions, Jake remembers everything. Mia really did cure her cancer with the secret (a type of fungus) given by the tribe's shaman! However, the Omolú company took this fungus, tested it in a lab without caution, and released a highly deadly ancient virus hidden within it—a virus to which the natives were immune. Half the world's population begins to die from this virus. Governments collapse. Mia is sick again, not with cancer, but as a victim of this new virus released into the world because of her husband's greed. Jake terrifyingly realizes his goal isn't just to save Mia, but to create a 'Cure/Antidote' from the Yabahuaca to save the world and redeem his soul. Voice of Mia on the radio is an massive hallucination.

Jake enters the final laboratory and attempts to synthesize a cure by mixing infected blood vials with various jungle properties. If the player successfully places a live poison dart frog into the analyzer alongside the infected blood (Good Ending), the machine returns '100% Antibody Found'. Jake takes the cure, gets extracted via helicopter, and brings mankind its only hope for survival. Mia is already dead, but Jake finds redemption. If the player leaves without finding the cure (Bad Ending), Jake loses his sanity. The cycle resets. He wakes up at the beginning of the jungle crash site, trapped in an endless nightmare known as the Green Hell.