Atomic scientist/pilot Doug Martin is missing after his plane crashes on an reconnaissance mission after a nuclear test. Miraculously appearing unhurt at the base later, he is given sodium amethol, but authorities are skeptical of his story that he was captured by aliens determined to conquer the Earth with giant monsters and insects. Martin vows to use existing technology to destroy them.
A scientist develops a formula which will cause animals to regress to the form of their primitive ancestors, and tries it on himself with disastrous results.
A mad scientist, Dr. Aranya (Jackie Coogan), has created giant spiders in his Mexican lab in Zarpa Mesa to create a race of superwomen by injecting spiders with human pituitary growth hormones. Women develop miraculous regenerative powers, but men mutate into disfigured dwarves. Spiders grow to human size and intelligence.
Dr. Paul Carruthers is frustrated because he thinks his employers, Mary Heath and Henry Morton, have cheated him out of the company's profits. He decides to get revenge by altering bats to grow twice their normal size and training them to attack when they smell a perfume of his own making. He mixes the perfume into a lotion, which he offers as a gift to Mary and Henry. When they turn up dead, a newspaper reporter decides to investigate.
Dr. Bernard Adrian is a kindly scientist who seeks to cure a young woman's polio. He needs human spinal fluid to complete the formula for his experimental serum. Meanwhile, a vicious circus ape has broken out of its cage, and is terrorizing the townspeople. Can there be a connection?
The second and final Grand National Pictures film to feature The Shadow, played again by Rod La Rocque. In this version, Lamont Cranston is an amateur detective and host of a radio show with his assistant Phoebe (not Margo) Lane. Cabbie Moe Shrevnitz and Commissioner Weston also appear.
The story of a century: a decades-long second World War leaves plague and anarchy, then a rational state rebuilds civilization and attempts space travel.
James Houghland, inventor of a new method by which television signals can be instantaneously sent anywhere in the world, refuses to sell the process to television companies, who then send agents to acquire the invention any way they can. On the night of his initial broadcast Houghland is mysteriously murdered in the middle of his demonstration and it falls to Police Chief Nelson to determine who the murderer is from the many suspects present.
Dr. Forti carries out strange experiments, assisted by his son Pablo. They embark on an expedition to the jungle. Eight years later Forti returns without his son but strange things start to happen in the old house where they live.
Clyde Beatty, an animal trainer and circus star, leads a search for his missing girlfriend and her father who were on an expedition looking for a lost tropical island. Using a dirigible as his mode of transportation, Beatty and his band head off in search of the missing explorers only to crash their airship on the same island their friends are located. Battling wild animals and a gang of greedy men searching for gold, Beatty and his party must rescue his girlfriend and father all the while trying to escape their jungle island. Feature version of the same-title serial of the same year, with refilmed sequences substantially altering the plot and characters of the original chapterplay.
In a futuristic city sharply divided between the rich and the poor, the son of the city's mastermind meets a prophet who predicts the coming of a savior to mediate their differences.