An expedition to Obelisk Island by Mr. Funazu uncovers a baby monster, who hatches from an egg in a massive cavern located underneath the island's volcano. The natives plead with the skeptical scientists not to take the baby away, lest it anger the baby's parents. Sure enough, despite the warnings the visitors callously ship the hatchling back to Japan. Soon, within the caverns, the adult Gappas rise from the underground waters beneath the volcano, destroying everything in their path.
The parents storm across Japan, destroying all in their wake, but their assault ceases once they recover their child. Mercifully, they relent, and depart to return to Obelisk Island.
- Main article: Baby Gappa/Gallery.