The story

The storyline begins in the near future, as referenced from the mid-1960s. In episode 22, "My Home Is Earth", it is definitively established that the series takes place in the early 1990s, as a plaque shown at the end of the episode displays the current year as being 1993. Sinister aliens and giant monsters constantly threaten civilization during this period. The only Earth organization equipped to handle these disasters is the Science Special Search Party (SSSP), a special police force with branches all over the world, and equipped with high-tech weapons and vehicles, as well as extensive scientific and engineering facilities. The branch of the Science Patrol that is focused on in the series is located in Tokyo, Japan. Led by Captain "Cap" Muramatsu (shortened to "Captain Mura" in the dubbed English-language version), the Science Patrol is always ready to protect the Earth from rampaging monsters, but sometimes finds itself overmatched. When the situation becomes desperate, Hayata, the Patrol's most capable member, holds the key to salvation in the form of a power-object called a "Beta Capsule", which, when ignited, allows him to transform secretly into the amazing, super-humanoid-powered giant from space—Ultraman.

While active as Ultraman, Hayata's human body goes into a type of deep coma, reviving only after the threat has been neutralized and Ultraman willingly departs. Victory is never assured, however, as Ultraman's powers—his very life force—comes from rapidly depleted, stored solar energy. At the beginning of each transformation from Hayata-to-Ultraman, the warning light on the giant's chest begins as a steady blue color. Yet as Ultraman exerts himself, the Color Timer changes to red, then blinks—slowly at first, then with increasing rapidity—as his energy reserves get closer to exhaustion. As the voice-over narration reminds the viewer—beginning with episode 2 and for each episode thereafter—if Ultraman ever reaches the point of total energy depletion, he "will never rise again."

Per the DVD set from BCI Eclipse (in episode 39, "Farewell Ultraman"), in the original subtitled version, Ultraman fights an enemy called Zetton, who employs a weapon Ultraman had not expected—one which damages his Color Timer and disables his ability to measure his power supply. As a result, Ultraman stays in his form too long and collapses into a dormant state. Fortunately despite this loss, the Science Patrol's members were able to defeat Zetton on their own. When Zoffy, Ultraman's superior, came to retrieve the fallen hero, Ultraman pleads for Hayata's life and offers his life completely, so that Hayata may live as a normal man. Zoffy then says he brought two lives and that he will give one to Hayata. He then separates them, giving Hayata new life, but Hayata seemed to have no memory between the time he first hit Ultraman's ship and his standing outside Patrol Headquarters as he watched Zoffy take Ultraman home. This is a rather different finish to the series than the English dub which stated Ultraman would return and that Hayata retained his Beta Capsule as he awaited Ultraman's return.