The U.N.G.C.C. (United Nations Godzilla Countermeasure Center) recovers the remains of Mecha-King Ghidorah and construct Mechagodzilla as a countermeasure against Godzilla. Meanwhile, a giant egg is discovered along with a new monster called Rodan. The egg is soon found to be none other than an infant Godzillasaurus.

Mining engineer Shigeru investigates the disappearance and death of his fellow coworkers when prehistoric nymphs are discovered emerging from the mines. After an attack on the local village, Shigeru heads deeper into the mines only to make a more horrifying discovery in the form a prehistoric flying creature. Soon a second monster appears as the two converge in Fukuoka.

US dubbed and edited version of the Japanese film Rodan. A mining engineer investigates the death of his fellow co-workers and discovers prehistoric dragonfly nymphs emerging from the mines. As he heads deeper into the mines, he makes a more horrifying discovery in the form a prehistoric flying creature.