Through an experiment by Dr. Stewart with animal cells, a monster is created that is given the name Frankenstein. He is a gentle giant, but he escapes his guards and was supposedly killed on a mountain. After several years, a ship off the coast is attacked by a green monster, where the people think of Frankenstein. The green monster attacks the fortified country, in which the army is then called in for help. When a brown monster suddenly appears, Dr. Stewart understands that his Frankenstein was not killed, but has reproduced.
| Actor | Role |
|---|---|
 Frank MullenDr. Paul Stewart / sailor (voices) | Dr. Paul Stewart / sailor (voices) |
 Barbara LaneyAkemi Togawa / nurse (voices) | Akemi Togawa / nurse (voices) |
 Hal ArcherDr. Yuzo Mamiya / air traffic controller / JSDF soldiers / diver (voices) | Dr. Yuzo Mamiya / air traffic controller / JSDF soldiers / diver (voices) |
 Nick KendallMajor General Hashimoto / Professor Kita (voices) | Major General Hashimoto / Professor Kita (voices) |
 Warren RookeLt. Col. Kazama / reporter / radio announcer (voices) | Lt. Col. Kazama / reporter / radio announcer (voices) |
 Ralph PixtonHirai / JSDF staff officer / JSDF radio announcer / radio announcer / JSDF soldier (voices) | Hirai / JSDF staff officer / JSDF radio announcer / radio announcer / JSDF soldier (voices) |
 Barry HaighChief Izumida / JSDF officer / reporter (voices) | Chief Izumida / JSDF officer / reporter (voices) |