A team of anthropologists travel to New Guinea in search of the missing link in this routine adventure tale. The expedition is financed by Vancruysen (Paul Hubschmid) and lead by Dr. Sybil Greame (Susan Clark). Also on hand are Douglas Temple (Burt Reynolds) and the boozy Otto Kreps (Roger C. Carmel). The two men are on the lookout for phospherous. The party discovers a group that appears to behalf human and half ape. Otto entices the female creature Topazia (Pat Suzuki) with sandwiches. When phosphorous is discovered, the evil industrialist Vancruysen enslaves the primates to work in the mines. Otto, Topazia, and Douglas escape, but there quest is slowed by the stillborn birth of Topazia's child. Douglas tricks the doctor into signing the death certificate that claims the child was human, which forces a murder trial. Eaton (Wilfred Hyde-White) is the South African anthropologist and racist called on to judge the proceedings.