A new and deadly mutation, a plant-like creature known as Bacillus (who may have been inspired by Biollante), appears and begins wreaking havoc, prompting H.E.A.T. to call upon Godzilla. During the battle, Godzilla is seriously injured and rendered catatonic as the result of being injected with a highly dangerous form of mutated bacteria by Bacillus. In order to save their kaiju ally, Tatopoulos and Monique travel within Godzilla's body in order to carefully exterminate all of the mutant bacterium. Now fully healed, Godzilla attacks Bacillus anew, and eradicates the creature with his incendiary breath.
