The Science Patrol discovers that the culprit behind a baffling series of volcanoes, earthquakes and other natural disasters is actually a giant monster. When it heads towards Tokyo, only Ultraman can stop it.

Hayata and the other Science Patrol members are trapped by the malevolent alien invader Mefilas, who proceeds to briefly turn Fuji into a giant monster herself before resurrecting doppelgangers of Ultraman's previous enemies Baltan Alien, the Kemurian, and Zarab Alien.