Jack Shindo and Stanley Haggard are the first men to land on Mars. Upon arriving they are met with none other than the strange alien monster Gudis. As Gudis was slowly moving towards them a giant silver humanoid by the name of Ultraman Great came to the rescue. After Gudis pushed Great aside he killed Stanley as he tried to escape in the ship as Jack was trapped by a rock slide. Great quickly got back up and used Burning Plasma to knock Gudis down. Gudis fell dead by the Burning Plasma's true power, but not before he sent a virus to Earth. To save the humans of Earth Jack had become Great's human host and went to Earth.

The next day, Bogun appeared that was created by the Gudis's virus. Bogun changed his appearance from that of a tadpole to a gigantic brute rampaging through the United States. UMA was sent to destroy it, but only succeeded in annoying Bogun. It wasn't long before Jack used the Delta Plasma Pendant to turn into Ultraman Great. As the two clashed, Great seemed to have the upper hand until Bogun used poison gas. However, the ultra persevered and eventually used Burning Plasma to set Bogun on fire.

An ancient being living in stasis for millions of years Gigasaurus was frozen under the ice of the arctic until the Gudis virus began to warm up the arctic and Gigasaurus was soon discovered by UMA. One day his icy prison began to slowly melt and his cells began to reproduce at a bizzare rate. As a batch of cells was about to be examined Gigasaurus woke up and increased his size to break out of the storage facility he was held at. UMA sent it's fighters as the icy dinosaur monster as he was rampaging through the town and soon into the local transformers. Gigasaurus's freezing breath prevented UMA's fighters from getting close. That night while Gigasaurus was sleeping plans were being thought up to destroy the large dinosaur for good. That morning as Gigasaurus was heading for a local oil refinery a human infected by the Gudis virus was waiting for him to show up. Jack hijacked one of UMA's fighters to catch up with Gigasaurus to prevent him from getting infected. Before Jack's fighter crashed from Gigasaurus's freezing mist he turned into Ultraman Great. The two giants clashed against one another and before long Great managed to used Magnum Beam to use the dinosaur's own mist against him. After a moment of silence for the beast, Great soon destroyed Gigasaurus with Burning Plasma and flew off.