A severe typhoon, in 1972, completely destroys a research facility in the Sierra Madre Mountains of the Philippines, exposing wild animals to chemical reagents and enzymes. A pair of monkey-eating eagles, following their consumption of prey tainted with the enzymes, increase in size and aggression. They begin attacking domestic livestock in the town of Santa Teresa, forcing local hunters to drive them out from their rainforest home. The winged predators relocated to the Caraballo Mountains, where Marco Vega, a seventeen-year-old biology student, spots one diving to grab a prey on the ground. A fascinated Marco, along with his horse and dog, heads to the woods to track the predator. His trek across the frontier is not without danger but that doesn't lessen his resolve in locating the eagles' nest. Braving the elements, he runs into strange characters: treasure hunters seeking General Yamashita's alleged WWII fortune, and criminals tending a large marijuana farm. The armed drug traffickers chase him down the river until the teen ducks inside a rat-infested tunnel. Luckily for Marco, growing up in a mine has honed his skills in surviving inside the abandoned tunnel. He burrows through cave-ins that's blocking his way to freedom. Having eluded his pursuers, he discovers the eagles' nest on a cliff--but he's not so lucky this time. As he scales the rock wall to have a closer look at the nest below, the giant eagle sees him and attacks. Marco loses his foothold and falls to the ledge. He lives through the dangerous plunge, only to realize that he's stranded on the eagles' lair. He must find a means of escape before his meager food supply runs out. While Marco's interactions with the giant raptors are for his preservation, they also reveal his true intentions--to help in saving the majestic monkey-eating eagle he has come to care for.