Oil prospectors Rolf and Robert travel to an outpost in a jungle on the island of Mindanao. A rough landing damages the plane. Robert and Rolf find the abandoned remains of the original prospecting camp. They then find a rotting corpse and determine the prospectors were massacred by natives. Later, a member of the team, Swan, goes missing. The two prospectors and their pilot Charlie go into the jungle, and the pilot is killed by a booby trap resembling a large mace. Robert and Rolf then see Swan's remains being eaten by cannibals. After building a raft in order to float down river to get back to the airfield, the men are separated when the raft is destroyed after traversing rapids. Robert, lost in the jungle, eats poisonous mushrooms, which cause him to vomit and pass out. He awakens to find himself being poked and prodded with large spears wielded by the cannibals.