An ancient skeletal sauropod dinosaur, Stegon was in suspended animation beneath the ground of Japan. A construction crew managed to awaken Stegon. After spewing small amount of acid on one of the workers Stegon arose from one of the hills. MAT was quick to respond to the scene, but their attacks did little beyond annoying Stegon. Goh turned into Ultraman Jack and began to tackle the skeletal sauropod. While try as the ancient reptile did Stegon was of little match for Jack in hand to hand combat. Before Jack could finish Stegon off some near by children were yelling out to him not to kill Stegon. Jack simply used his paralysis beam, lifted Stegon, and turned his body into a constellation of stars just like the original Ultraman did with Gavadon four years earlier. The children were happy and MAT then left.
工事現場から巨大な恐竜の化石が発掘され、子供達は大喜び。作業を急ぐ現場責任者は化石を爆破するが、化石から強力な溶解液がにじみ出て、作業員を跡形もなく溶かしてしまった！しかも、爆発のショックで化石は怪獣ステゴンとして蘇るが、ステゴンに対する子供達の愛着を知っている郷と南は、ステゴンの討伐をためらう。
