As Kartin says, 'You can't have houses in space.' What then are those mysterious objects that have suddenly appeared far out on the planet routes? What connection do they have with 'the Shy Six Hundred', as Kemlo calls them, those strange, Earth-born visitors to Satellite K who are so chary of having their photographs taken?

Kemlo and his Space Scouts decide that the time has come for a little detective work and the boys are soon hot on the trail - a trail which is to lead them from the comfort and security of the satellite to a battle to the death twenty million miles out into the void.