(First Aired: November 13, 1966)
Screenplay by: Ryu Minamikawa and Tetsuo Kinjo
Directed by: Samaji Nonagase
One night, a mysterious radioactive fog settles over Tokyo, choking its denizens like poison gas. Science Patrol is called in to check it out, while Muramatsu is informed by Dr. Morita that this bizarre fog is from space and most likely artificial. The question is who made it?
While using their helmets radiation shields to protect themselves, Arashi and Ide spot a strange figure wandering through the deadly fog. Ide walks up to the person to take him to shelter and is unpleasantly surprised to find out that hes not human! Arashi and Ide chase after the being, but when they tackle him, they are left with only its robes. Looking above, they spot the being a scaly humanoid with a domed metal head climbing a building like a spider. Arashi shoots it, but it vanishes in thin air. Arashi reports this to HQ, but he and Ide are then knocked out by the being via a mysterious frequency. The being then contacts HQ, introducing himself as Alien Zarab and describing himself as an elder brother to humanity before breaking off, leaving the HQ team (Muramatsu, Fuji, Hoshino, and Dr. Morita) confused.
Meanwhile, Hayata travels through space in search of the fog's source and reports to HQ that he has found the Saturn Exploration Rocket, a rocket that departed Earth a month ago. Curious to know why its now so close to Earth, he tries to make contact with no results. The returning Arashi and Ide overhear this, prompting Arashi to ask what everyone was wondering minutes ago. The answer is given when Zarab suddenly appears in the Science Patrol HQ and tells them he took it back to Earth in the same manner an elder brother takes his unconscious younger brother to safety. Not totally trusting the alien but understanding that the way he refers himself as an older brother indicates he's a very advanced alien, Muramatsu asks if Zarab will clean up the radioactive fog for humanity, to which Zarab agrees to as a token of trust.
At Tokyo, Zarab removes the blanket of deadly fog with a few gestures. At the same time, the fog appears in space, where Hayata is still circling the Saturn Rocket. Hayata decides to head back to Earth as the fog has taken the rocket from his sight. On Earth, Zarab is invited to stay at Science Patrols guest room, where Ide shows him around. However, Zarab places his hand over Ides head and stuns him with mind control.
The following day, Arashi is managing communications at HQ while the rest of the team discusses about Zarab with the higher-ups in a top-secret meeting. Then, Fuji arrives with coffee, which Arashi gladly accepts, despite his confusion on why Fuji is still in the building. Upon a sip, he is knocked out by something in the coffee, and Fuji reveals herself to have been a disguised Zarab, who promptly takes over HQs communication system to hear the discussion. At the meeting, Hayata notices that Ide (who has been unnaturally stoic the whole time) has his communicator on for no apparent reason (being used by Zarab to listen, in actuality) and tears it off his uniform. Suspicious of Ides actions, Science Patrol conducts a study of his brainwaves after the meeting, finding out that hes under a sort of hypnosis.
The team (except Ide) returns to HQ, where they learn that the government has decided to bring Zarab under their protection. Muramatsu objects to this, as the Science Patrol computer is necessary to translate Zarabs native language. Thats when Zarab comes in with a radio-like device in his hands and the HQ computer begins to malfunction. Zarab tells the team that hes going with the Japanese government and the device he has is a translator with an atomic engine so strong that its radio waves damaged the computer. With that, Zarab leaves Science Patrol behind to ponder what his intentions are. Hayata suggests some investigating.
That night, the investigation begins. Hayata rests inside the Jet V-TOL while Arashi and Fuji witness Zarab fly off to space. Hayata follows suite, eventually finding the Saturn Rocket again. Believing Zarab to be inside, he puts on a spacesuit and heads for the rocket. Peeking through the rockets windows, he spies Zarab awakening unconscious crewmen in a state of hypnosis. Now understanding the aliens true goals, Hayata returns to the V-TOL and drives back to Earth. Suddenly, the V-TOL stops by itself and Zarab appears on board, making it clear that he was not oblivious to Hayatas presence. In his speech to Hayata, Zarab explains that he knows Hayata is Ultraman and the only thing standing between him and his scheme - world domination through sowing discord and distrust. With that, Zarab stuns Hayata with an alien frequency before teleporting himself and his prisoner off the reactivated V-TOL.
The pilotless V-TOL crashes into the middle of nighttime Tokyo and a sinister-looking Ultraman appears, destroying the city only to disappear just as quickly. While the authorities are discussing that oddity, Zarab appears to them to state that Ultraman and Science Patrol are the enemy. Leaving them behind to bicker some more, Zarab heads off to meet up with his prisoner Hayata, whom Zarab has tied up with alien bindings and left on the floor. The invader attempts to take the Beta Capsule, but is unable to find it. A frustrated Zarab leaves to continue his plans, and thats when Hoshino sneaks in through a window via rope with some tools to free Hayata. He also has the Beta Capsule, which Hayata left at HQ.
Outside, the sinister-looking Ultraman from earlier looms over Tokyo and proceeds to destroy everything around him. Science Patrol and the JSDF fight the evil Ultraman, while Hoshino manages to free Hayata when they find out that water dissolves the bindings. The freed Hayata instructs Hoshino to leave for safety, but the evil Ultraman spots the boy climbing down the rope. He grabs the boy and ponders what to do with him, while Hayata becomes Ultraman! The real Ultraman saves Hoshino before clashing with his imitator. A well-aimed Specium Ray forces the fake Ultraman to change back into a now giant-sized Zarab, who takes flight with Ultraman hot on his heels. Soon, Ultraman manages to kill Zarab with another Specium Ray before taking off again, while Science Patrol is relieved to know that Ultraman hasn't turned his back on humankind.