The fictional Commonwealth Space Project (CSP), based in Woomera, South Australia, is working to build a space station orbiting a thousand miles above the Earth's surface: Orbiter X. Planned to be a refuelling station for further space exploration, along with laboratories and other services, the CSP has launched the various components for the space station into orbit. But before construction can begin, the first assembly ship, Orbiter 1, is seemingly attacked and loses contact with CSP Control.

A second ship, Orbiter 2, piloted by Captain Bob Britton (John Carson), sent to rescue the first crew finds Orbiter 1 deserted and the spacecraft's log missing. Orbiter 2 is also attacked by a UFO and Flight Engineer 'Hicky' (Barrie Gosney) seriously injured. With their spacecraft crippled, the crew have no alternative but to abandon ship and place themselves at the mercy of their attackers. Once aboard the UFO, they meet Commander Gelbin (Arthur Lawrence), the deputy leader of the Unity organisation: a group of technocrats who plan to use Orbiter X themselves and create a New World Order.