Captive Wild Woman

Trainer Fred Mason returns from a safari with animals for the circus of his employer John Whipple. Among the new animals, Chila is a gorilla with surprisingly human habits. Mason says that this is the most affectionate animal he has ever encountered in the jungle. Mason's fiancee Beth Coleman meets him at the pier. She tells him about the health problems that her sister Dorothy has recently faced. Beth took her sister to see Dr. Sigmund Walters, an endocrinologist. Dorothy is currently being treated at the Walters Crestview Sanatorium.

Fred and Beth arrive at the circus, and Dr. Walters also pays a visit there. He is extremely interested in Chila and asks about the possibility of buying her. Whipple replies that the gorilla is not for sale. Returning to his laboratory, Walters discovers that his latest experiment has led to the death of a laboratory animal. He decides that he needs larger animals with a "will to live." Walters turns to a former circus worker offended by his employer with a proposal to steal a Chill. After the monkey cage is loaded into a truck, the scientist callously pushes the accomplice into the arms of the gorilla and impassively watches his death.

Back at the lab, Walters and assistant Miss Strand transplant Dorothy's gland tissue to the child. Ms. Strand says that Walters had previously performed similar operations: transplanted guinea pig glands to a rabbit, and frog glands to a mouse. Each time it led to the death of the donor. To the nurse's horror, the monkey turns into a human. Informing the doctor that she cannot allow him to continue the experiment, Miss Strand declares that at best he will get a creature "with the forms of a man, but the instincts of an animal." Dr. Walters comes to the conclusion that in order to successfully complete the experiment, he will need to put a human brain into his creation. To do this, he plans to use Miss Strand's brain. The brain transplant is successful, and as a result of all the manipulations, a young woman of exotic appearance appears in the laboratory, who does not remember anything about her previous life. Walters calls her Paula Dupri and brings her to the circus for her first public appearance. Mason, who trains lions and tigers, falls, and the animals pounce on him. Paula bursts into the cage and saves him from the ferocious cats, who show unnatural fear and retreat in front of her. Puzzled, Mason offers the girl to take part in his circus act.

After the dress rehearsal, Paula becomes jealous of Mason's fiancee. She goes to the dressing room and after a tantrum begins to turn back into an animal. That night, she climbs into Beth's window, planning to kill her, but instead attacks another woman. Already in animal form, she returns to Walters, and the doctor realizes that in order to return her to human form, a second operation is necessary. He can use Dorothy again to get gland tissue, but he will need another donor to replace Paula's damaged brain.

In desperation, Dorothy calls Beth and tells her about her fear of Dr. Walters and the upcoming operation. Beth rushes to the sanatorium to help her sister. There she is grabbed by a distraught scientist who is going to use her as a brain donor. However, she turns out to be resourceful and releases an angry monkey from the cage. Chila kills Walters and escapes from the lab, leaving Beth and Dorothy unharmed.

Performing his act with wild animals alone, Mason finds himself locked in a cage. The performance is interrupted by a powerful storm, and the animals, distraught with terror, attack the trainer. Chila comes to his aid again and takes him to a safe place. Unfortunately, one of the policemen guarding the circus misunderstands the gorilla's intentions and kills Chila.