Renowned explorer Frank Buck is commissioned by the U.S. government to investigate the recent flurry of tiger attacks in the Far East. In Penang, Frank consults with United Nations representative Peter Jeremy, and learns that the tiger attacks have resulted in an interruption of rubber production, which is potentially damaging to the Allied war effort. With his native guide, Ali, Frank heads for the Territory of Damang Nog, where the locals are convinced that the tigers have become "t'jindaks," animals inhabited by evil human spirits, and that their souls are being invaded by the Japanese. Frank and Peter work out of Geoffrey MacCardle's rubber plantation, which is overseen by Tom Clayton. Posing as a zoo representative, Frank makes a contract with animal exporter Henry Gratz to use his cages for trapped tigers. Unknown to Frank, Gratz and local physician Dr. Lang have been poisoning tigers with a substance that makes them crazed, and then releasing the animals near plantations. After Frank and Peter find a poisoned dart in a tiger they have trapped, they bring the dart to Geoffrey's granddaughter Linda, who is Lang's assistant, to determine the poison content. Lang steals the dart, however, and warns Gratz that Frank is on their trail. When another tiger is captured, Frank and Peter recognize it as a cat they saw being tortured at Gratz's. Gratz claims that his tiger had escaped, but Frank realizes that a bamboo sheath he sees on the floor of Gratz's office was used to make the poisoned dart. That night on the plantation, Gratz's assistant Takko releases a deadly leopard into Linda's room. Frank rescues Linda, and again recognizes the cat as one he had trapped and was keeping at Gratz's. After further evidence points to Gratz's guilt, Gratz tries to kill Frank and Peter, but is trampled to death by a herd of frightened elephants. After Linda determines that the poison from the darts is synthetic, Lang reveals that he has been working for the Nazis in an effort to harm the Allied war effort. Frank then grabs Lang's gun and narrowly avoids being hit by one of Takko's poisoned darts, which instead strikes Lang. Lang is killed by his own poison, and Takko is killed by Ali. After rounding up the tigers, Frank leaves the jungle.