Iria, an interstellar bounty hunter, arrives on Earth to prepare a trap for Zeiram, an incoming alien convict. She plans to trap Zeiram in an alternate dimension called the Zone, which mimics the surrounding environment but without any innocents in the way, so she can hunt and capture him without any casualties. Her preparations are flagged by a power company, which sends two handymen, Teppei and Kamiya, to investigate. They find Iria’s hideout as Zeiram enters the atmosphere. The commotion caused by Zeiram’s landing causes them to accidentally activate the transporter equipment, sending Teppei into the Zone with Zeiram.

Iria takes Kamiya into the Zone with her to rescue Teppei and capture Zeiram. She succeeds in trapping Zeiram in a holding cell, but not before Zeiram clones a minion to attack her. Iria tries to teleport Teppei and Kamiya outside the Zone but accidentally sends herself and the minion back instead. The minion destroys the teleporter equipment before Iria kills it, leaving Teppei and Kamiya stranded in the Zone. Another cloned minion appears and attacks Teppei and Kamiya. In fighting it off, they accidentally release Zeiram from its holding cell, and they are forced to flee.

Iria realizes that the Zone’s maintenance program was corrupted by the minion’s attack, meaning that the Zone will disintegrate in a matter of hours, taking Zeiram, Teppei and Kamiya with it. Iria manages to teleport back into the Zone and obliterates Zieram, leaving only its most vital organ intact. She has Teppei and Kamiya teleported out of the Zone, followed by Zieram, which breaks loose and wreaks havoc on Iria’s equipment. As Zeiram attempts to kill Teppei, Kamiya manages to fix the teleporter just in time for Iria to appear and finally kill Zeiram.