An unseen monster attacks San Javier, Peru. Believing it to be Godzilla, G-Force heads for Peru. Helzer is the only one who expresses the opinion that it may be another monster that is responsible. G-Force questions the village survivors and doubts begin to rise. There is no radioactivity in the area. G-Force finds a deep fissure far inland which is where the monster's trail leads. They determine that it is a new monster and name it Burtannus after Burton Helzer.
Kino and Take' don jet packs and descend into the fissure while the rest of G-Force heads back to their ship to get supplies for the villagers. Suddenly they see the Peruvian air force engaging Godzilla on the coast. Godzilla is headed inland, hunting the other monster. Back in the fissure, Kino and Take' discover a pair of baby monsters.
Soon the adult Burtannus shows her angry face. Kino and Take' blind her with their lights and race away down the tunnel. They escape just as seawater rushes into the tunnels. Godzilla has dug his way into Burtannus' lair. The two monsters are soon battling in the coastal waters. Godzilla abandons his fight with Burtannus as the other monster swims out to sea with her young. Godzilla follows suit, only headed in a different direction.