"A distant star, a dying planet. A race of desperate men seeking another home, another world to take over. One man is trying to stop them, a man not of this world..."

Simon King (Jon Finch) is sent to earth as a sort of intergalactic secret agent to track and stop any invasion by the Centaurans who have the intent of taking over Earth. This series only lasted ten episodes, one of which was never transmitted. Only four episodes have survived and remain in the BBC's archive.