A businessman/publisher sends a team to the South Pacific island of Obelísk to collect exotic animals and birds for the tropical-themed Playmate Park he is planning to open in Tokyo. While there, an earthquake topples a statue that has been hiding the entrance to a steaming cave. Inside, the team observes a gigantic egg hatch. Yet another earthquake dislodges the egg from its resting spot. It rolls down a slope, hits some large rocks that crack the shell, and releases a small winged baby bird-like reptile. Thinking this is a sensational discovery, the team cages the baby to ready it for transport back to Japan. The native chief begs the group not to remove the baby from their island; it will make Gappa angry and they will be destroyed. The Japanese ship leaves with the baby and, unfortunately, that does not sit well with its parents. They suddenly surface on Obelísk, wreak a bit of havoc on the natives and quickly depart for Japan. They come ashore at a port city, where the two adult-sized Gappas destroy everything in their path at will. Tanks and aircraft are unable to stop them. An attempt to lure them out into a lake so that they can be targeted with rockets also fails. A female photographer and a native boy from the island convince officials to let the parents take the baby back to Obelísk. They play a recording of the baby over a loudspeaker system at the airport to attract the attention of the parents. They arrive to escort their offspring back to Obelísk. Everything will be fine now.
—Garon Smith