In 2038, a gang of scavengers infiltrate an industrial complex on a island within a prohibited zone. They are looking for the element Texmexium, which is rare and very valuable. The scavengers are killed off by the automated defenses, until only Brooklyn, the group's mechanic, is left.

He discovers a stranded Texas Air Ranger and two children living among the complex's rubble. Together, they must destroy the Kyron-5 computer in order to escape and warn humanity. Brooklyn discovers a GUNHED (from "Gun UNit Heavy Elimination Device") combat robot left over from when a battalion of Gunheds were sent to destroy Kyron-5. Brooklyn works to restore it to operation. Meanwhile, Babe, one of the scavengers killed earlier, has been transformed into a bio-droid and is seeking out Sergeant Nim and the Texmexium she stole.

In order to save her and destroy Kyron-5, Brooklyn must overcome his fear of flying and pilot the GUNHED to the top of the complex's tower. The computers single large defence is the robotic Aerobot.

Note: The 2024 revamped edition has new material