At the rock hovel home of Abner Tasupi (George Clutesi), a 92-year-old high priest of the Masakai, tribal deputy Youngman Duran (Nick Mancuso) finds the old man trying to bring the world to an end by summoning Yewah, the monster god of the Masakai who guards the gates of life and death. Called to the Mamoa ranch, Duran is puzzling over the strange razor-sharp wounds and smell of ammonia coming from a dead horse when a helicopter soon arrives bearing Walker Chee (Stephen Macht), a wheeler-dealer politician from the neighboring Pahana tribe, accompanied by a veterinarian who underscores Duran's observations as he takes samples to determine what killed the animal. After going to see Anne Dillon (Kathryn Harrold), a health service nurse with whom he's romantically involved, Duran returns to Abner's shack to find the old man dead, his flesh stripped raw like that of the Mamoa ranch horse. Meanwhile, when Anne takes four foundation missionaries out on a camping trip, as they are gathered around an evening campfire, they hear a strange keening sound just before thousands of bats come swarming down upon them. Hearing that two women in the missionary's party have been found dead in the desert, Duran starts off in pursuit, hoping to save Anne. When his vehicle overheats and he is rescued by an English biologist Phillip Payne (David Warner), they set out together and find Anne, the sole survivor, nearly dead of thirst. Explaining how, the night before, he set up a trap and injected a tracking device into one of the bats, Payne carries his equipment up to limestone dome where he uses an electronic signal to locate the colony's daytime nesting place. As he prepares to drop a tank of deadly cyanide gas into the cavern, Payne slips and tumbles down into the opening where he's left dangling from a rope. As Payne's life hangs by a thread, Duran desperately attempts to save him and put an end to the deadly menace lurking within.