Beth Colman (played by Evelyn Ankers) is delighted when her boyfriend, circus executive Fred Mason (played by future Gunsmoke doc Milburn Stone), returns home from a successful trip to Africa capturing animals for the circus. In addition to lions and tigers, Mason has formed an unusual bond with a female gorilla, Cheela, who he is already training.
John Whipple (played by Lloyd Corrigan) is the over-taxed, hand-wringing circus owner. Due to business problems, Whipple reluctantly allows Mason to try his hand with a new act: lions and tigers in the arena at the same time!
Meanwhile, Beth's sickly sister Dorothy (played by not-yet-famous Martha Vickers) has been taken to an expert glandular doctor. Dr. Sigmund Walters (John Carradine in his first starring role) diagnoses Dorothy with a glandular condition involving sex hormones, and admits her to his sanitarium.
We learn that in his glandular experiments, Dr. Walters has been able to transform animals into new species and genders, but the animals die due to their small size and lack of intelligence. His faithful assistant is Nurse Strand, played by Fay Helm.
Dr. Walters is invited to tour the circus facilities, where he learns about Cheela the ape. Recognizing her potential as a lab animal, he arranges with a disgruntled circus employee to steal Cheela. We get our first hint of Dr. Walter's insanity when he kills his accomplice; then when Nurse Strand objects to using Dorothy's blood/hormones to experiment on Cheela the ape, Dr. Walters realizes he'll need to transplant part of a human brain into Cheela to give her greater intelligence – and Nurse Strand is conveniently on hand to donate a brain!
The treatments work, and Cheela the ape transforms into beautiful but mute Paula Dupree (played by Acquanetta) – and she turns out to be useful at the circus, where she has a mysterious power to control wild animals. But will Paula Dupree be able to control her bestial nature in a human world?
In order to make this movie, they reused circus footage from a ten-year-old movie, The Big Cage. Milburn Stone was cast in his role because he best matched the height and build of the animal tamer from that movie. They do a good job of matching old movie segments with new movie segments, but the film quality is noticeably different.
There are also some excellent special effects. Ray Corrigan (uncredited) dons a gorilla suit to play Cheela; we also get transition shots as Cheela transforms into human form.
The two stand-out stars in this movie are John Carradine as the mad scientist, at the beginning of a long career in horror; and Acquanetta, billed by the studio as "the Venezuelan Volcano" though actually half-Arapaho (Native American), who looks lovely in her short skirts.
The rest of the cast were adequate. Martha Vickers only gets a few lines late in the movie – she will obtain fame soon, playing a 'bad kid sister' next to Lauren Bacall in The Big Sleep.
Believe it or not, this movie would go on to spawn two sequels.
I enjoyed this movie quite a bit. Does anyone make a mini of John Carradine as a mad scientist, or Fay Helm as a faithful nurse?