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Susan Stevenson (Ursula Andress) and her brother, Arthur (Antonio Marsina), travel to New Guinea in the hopes of finding her husband, who has gone missing for three months. The pair encounter anthropologist Dr. Edward Foster (Stacy Keach), who agrees to lead a jungle expedition in search of the missing man. As mantraps and other jungle dangers slowly whittle away the search party, Foster becomes convinced that Susan's husband is somewhere on the tiny coastal island of Roka, home to the sacred island of Ra Ra Me. En route to the mountain, the party is captured by the Puka, a Stone Age tribe long considered extinct. Foster reveals that the tribe is cannibalistic, having been captured and forced to consume human flesh years before. This gruesome news, however, pales before Susan's discovery of her husband's fate -- a fate that will surely befall the entire party if they are unable to escape.