In Colombia, Rudy Davis, Gloria Davis, and their friend Pat Johnson set out on a grueling journey into the rainforest to test Gloria’s theory that cannibalism is a myth. The trio quickly encounters a drug dealer, Mike Logan, and his business partner, Joe Costolani. Joe is badly wounded, and Mike insists that cannibals attacked them as a cover for their own crimes. As night falls, Gloria vanishes, and Rudy Davis stumbles upon a native village while searching for her.
Because of Joe’s injuries, the travelers are drawn to the nearly deserted village and decide to stay. Mike seduces Pat, who is portrayed as naïve and eager for something beyond their perilous trek. In a cocaine-fueled rage, he pressures Pat to kill a native girl. She cannot go through with it, and Mike takes the life himself. In his dying moments, Joe reveals that he and Mike were responsible for the escalating aggression from the cannibals, driven by a plan to exploit the region for emeralds and cocaine, preying on the locals’ trust in white outsiders. One day, while high on cocaine, Mike brutally tortures and murders their native guide, an atrocity done in full view of the tribe. A badly charred body—once misidentified as another guide—is revealed to be the native. Mike had kidnapped a native girl to guide them out of the jungle, but the outsiders are tracked and attacked.
After the native girl’s murder, the cannibals reach a breaking point and begin hunting the outsiders. Joe dies from his wounds, and his body is found and cannibalized by the natives in full view of Rudy Davis and Gloria, who hide from the danger. Mike and Pat abandon the others, but everyone is captured and forced into a cage. The prisoners are made to watch Mike endure torture and beating, including a brutal moment where his penis is sliced off with a large machete-like knife and eaten by a native villager. The captives are moved to another village, but Rudy manages to escape. He is caught in a jungle booby trap, his bleeding wounds drawing piranhas, and the natives shoot him with a poisoned dart, ending his life before the others.
Pat and Gloria are confined in a hole in the ground, while Mike remains in a separate cage. A native man, whom Pat had previously saved from Mike’s aggression, lowers a rope into the hole so the women can escape. Mike digs out of his cage, drives the helper away, and cuts the rope, ensuring the women cannot escape. He then flees into the jungle, attempting to signal a search plane, but is recaptured. The natives amputate one of his hands and drag him back to the village. A search plane arrives, but the natives convince the rescuers that the outsiders’ canoes capsized and were eaten by crocodiles.
As the plane departs, Pat is bound, stripped to the waist, and hooks are driven through her breasts to hang her alive. Gloria can only watch Pat’s slow, painful death. Meanwhile, Mike’s head is placed in a crude device, and the top of his skull is removed so the natives can feast on his exposed brain. A sympathetic native later frees Gloria, guiding her through the jungle only to fall prey to a trap. Gloria eventually meets a pair of trappers who take her to safety. Rather than tell the truth, she recounts the natives’ lie that the others were eaten by crocodiles.
Back in civilization, Gloria, deeply scarred by the experience, writes and publishes Cannibalism: End of a Myth, a book that distorts events to support her theory and conceal the brutal ordeal she endured.
